• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.40-47
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• 2017

Dust explosion hazards are always present when combustible dusts are manufactured or handled in the process. However, industries is experiencing difficulty in establishing chemical accident prevention measures because of insufficiency of information on dust explosion characteristics of combustible dust handled in industry. In this study, we investigated experimentally dust explosion characteristics of two kinds of multi-walled carbon nano tubes (MWCNT) different in particle size distribution and examined classification of dust explosion hazardous area for MWCNT manufacturing or handling process by applying the NFPA 499 code. As a result, $P_{max}$, $K_{st}$, LEL, MIE and MIT of MWCNT 1 having $124.2{\mu}m$ median diameter are obtained 6.3 bar, $56bar{\cdot}m/s$, $125g/m^3$, over 1000 mJ, and over $650^{\circ}C$. $P_{max}$, $K_{st}$, LEL, MIE and MIT of MWCNT 2 having $293.5{\mu}m$ median diameter are 6.2 bar, $42bar{\cdot}m/s$, $100g/m^3$, over 1000 mJ, and over $650^{\circ}C$, respectively. MWCNT 1, 2 are not categorized as combustible dust listed in the NFPA 499 Code for classification of dust explosion hazardous area because explosion severity and ignition sensitivity of MWCNT 1, 2 are below 0.35 and 0.01, respectively.

• Korean Journal of Food Science and Technology
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• v.28 no.3
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• pp.506-513
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• 1996

Soybean hull was microparticulated at cut-off wheel speed of 9,000 rpm and air-classified into fine and coarse fraction at air classifying wheel speeds (ACWS) of 10.000, 15,000 and 20,000 rpm. respectively. Proximate analysis of the coarse and fine fractions of the microparticulated/air-classified soybean hull showed that ash, protein and lipid were enriched in the coarse fractions and carbohydrates in the fine fraction. Dietary fiber were enriched in coarse fractions and dietary fiber and dietary fiber content increased with decreasing ACWS. Mean particle size of fine fractions ranged from $3.1{\mu}m\;to\;5.5{\mu}m$ that of coarse fractions ranged from $9.9{\mu}m\;to\;20.0{\mu}m$ and both increased with decreasing ACWS. The particles were mostly oval-shaped regardless of the fractions. Generally the fraction of low ACWS showed higher viscosity. In water holding capacity, oil absorption and emulsion capacity, there was significant difference between coarse and fine fractions while there was no significant difference as a function of different ACWS. Oil absorption of flying batter was decreased significantly in the fraction of ACWS 15,000. when cakes and cooking were prepared partially substituted with soybean hull fraction, there was no significant changes on their physical and sensory properties up to 10% substitution.

• Journal of the Korean earth science society
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• v.43 no.6
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• pp.762-776
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• 2022

The purpose of this study was to determined the conceptual structure used by earth science teachers to classify metamorphic rocks as well as the criteria applied in the process of classifying metamorphic rocks. To this end, the researchers collected verbal data uttered in the process of classifying metamorphic rock using think-aloud from 21 earth science teachers in middle and high schools in Jeollabuk-do, Republic of Korea. The collected verbal data were analyzed using the semantic network analysis method, and the following results were obtained. First, in the process of classifying metamorphic rocks, earth science teachers classified them based on characteristics such as color, compositional minerals, and particle size, which can be generally observed in rocks, and foliation that appears in metamorphic rocks. Second, earth science teachers recognize the classification criteria for metamorphic rocks and focus on metamorphism such as contact metamorphism or regional metamorphism. However, there were cases where rocks were mistakenly classified through incorrect identification. Therefore, it is necessary to provide sufficient observational information about, and experience of, metamorphic rocks to enable earth science teachers to recognize and relate to the scientific process of identifying metamorphic rocks through the phenomena observed.

• Economic and Environmental Geology
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• v.47 no.5
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• pp.479-488
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• 2014

Naturally occurring asbestos (NOA) from disturbance of rocks and soils has been overlooked as a source of exposure that could potentially have a detrimental impact on human health. But, few researches on mineralogical characteristics of NOA occurred in soils have been reported in Korea. Therefore, the objective of this study was to investigate the mineralogical characteristics of NOA occurred in soils at Daero-ri area, Seosan, Chungnam Province, Korea. Sedimentation method was used for particle size separation of the asbestos-containing soils. XRD and PLM analyses were used to characterize mineralogical characteristics and mineral assemblages in soils. SEM-EDS and TEM-EDS analyses were used to characterize mineral morphology and chemical composition. Particle size analyses of the asbestos-containing soils showed they were composed of 26-93% sand, 4-23% silt and 3-70% clay. Soil texture of the soils was mainly sand, sandy loam, sandy clay, and clay. PLM analyses of the soil showed that most of the soil contained asbestiform tremolite and actinolite. The average content of asbestos in the soil was 1.5 wt. %. Therefore, the soil can be classified into asbestos-contaminated soils based on U. S. Environmental Protection Agency classification (content of asbestos in contaminated soil > 1%). Morphologically different types of tremolite such as long fibrous, needle-like, fiber bundle, bladed and prismatic forms co-existed. Prismatic tremolite was dominant in sand fraction and asbestiform tremolite was dominant in silt fraction. This study indicates that the prismatic form of tremolite transform gradually into a fibrous form of tremolite due to soil weathering because tremolite asbestos was mainly existed in silt fraction rather than sand fraction.

• Korean Journal of Soil Science and Fertilizer
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• v.6 no.2
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• pp.75-81
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• 1973

The morphological, physical, and chemical properties of Sonjeong series derived from acidic crystalline rocks are presented. Also it deals with the genesis and classification of the Songjeong series. Morphologically these soils have brown to dark brown loam A horizons and yellowish red to red clay loam Bt horizons with moderate, medium subangular blocky structure and thin patchy clay cutans on the ped faces. C horizons are very deep, yellowish red to yellowish brown fine sandy loam or sandy loam with original rock structure. Physically distribution of particle size indicates that clay increases with depth up to argillic horizons but below the argillic horizons clay content decrease. The moisture holding capacity is fairly good in Songjeong soils. Chemically soil reaction is strongly to very strongly acid throughout the profile and content of organic matter is less than 1 per cent except A horizons. Cation exchange capacity ranges from 5 to 9 me/100g of soils and base saturation is less than 35 per cent throughout the profile. The natural fertility of Songjeong soils are usually low. It needs lime, organic matter, and heavy application of fertilizer for the crop land. These soils occur temperate and humid climate under coniferous, deciduous, and mixed forest vegetation. Songjeong soils are classified as Red-Yellow Soils. Characteristically Songjeong soils are similar to Red-Yellow Podzolic soils in the United States but lack of A2 horizons and are quite liket Red-Yellow Soils of the Japan. According to new classification system which is 7th approximation of USDA Songjeong soils can be classified as fine loamy, mesic family of Typic Hapludults and in the FAO/UNESCO project World Soil Map as Orthic Acrisols.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.5
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• pp.916-921
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• 2011

This study was carry out on a Jang-Won series (fine loamy, mixed, mesic family of typic fragipan) that were established and classified as a fragipan soil in Korea. The morphological, physical, chemical and minerals characteristics of Jang-Won series were studied to determine the genesis of fragipan soils in natural environment. Each sample was analyzed for its physical, chemical and mineralogical characteristics. The particle size distribution of samples was measured using pipette method. Clay minerals were investigated on parallel-oriented specimens of the clay fraction ($<2{\mu}m$) from each horizon, separated by sieving and centrifugation, using X-ray diffraction (XRD) analysis. Micromorphological observations were made on thin sections prepared from soil blocks impregnated with Crystic Resin, cut and ground to less than $30{\mu}m$ in thickness, and finally polished with diamond paste. Most horizons have pH values in the range of fewer than 5.0 and have very low base-saturation values. Their textural classification ranges from silt loam to loam, the lower horizons being the finer. The clay fraction revealed the occurrence of illite, kaolinite, chlorite and vermiculite. The micro-morphological analysis carries out thin sections from each soil profile. The silt concentrations occur as extremely dense and homogenous bands or zones of silt-sized materials, brownish in colour in plane-polarized light and anisotropic in cross-polarized light, surrounding or adhering to skeleton grains. The genesis of fragipan in the Jangweon series assumed composition of clay fraction rather than silt concentration. Therefore, this results suggested an authentic interpretation which Jangweon series is classification as Typic Fragiochrepts.

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.5
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• pp.385-392
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• 2009

This study was conducted to reclassify Namweon series, black volcanic ash soils, in Jeju Island based on the second edition of Soil Taxonomy : A Basic System of Soil Classification for Making and Interpreting Soil Surveys. Morphological properties of typifying pedon of Namweon series were investigated and physicochemical properties were analyzed according to Soil Survey Laboratory Methods Manual. The typifying pedon of Namweon series has black (10YR 2/1) silt loam Ap horizon (0~11 cm) and black (10YR 2/1) silt loam BA horizon (11~72 cm). Bw horizon (72~100 cm) is very dark brown (10YR 2/2) silt loam. That occurs on lava plain derived from volcanic ash materials. The typifying pedon contains 5.2~6.4% oxalate extractable (Al + 1/2 Fe), over 85% phosphate retention, and lower bulk density than $0.90Mg\;m^{-3}$. Ap, BA, and Bw horizons of the pedon have andic soil properties. That can be classified as Andisol. The typifying pedon has an udic soil moisture regime and has a 1,500 kPa water retention of 15% or more on air-dried samples throughout all horizons, and can be classified as Udand. Ap and BA horizons (0~72 cm) have a color value, moist, and chroma of 2 or less, melanic index of 1.70 or less, and 6% or more organic carbon. That meets the requirements of melanic epipedon. That keys out as Melanudand. That has more than 6.0% organic carbon and the colors of mollic epipedon throughout a layer 50 cm or more thick within 60 cm of the mineral soil surface.. Thus, that keys out as Pachic Melanudand. The pedon has a fine-earth fraction that has a water content at 1,500 kPa tension of 12% or more on air-dried samples and has less than 35% (by volume) rock fragments. Thus, the substitute for particle-size class is medial. That has a sum of 8 times the Si (percnt by weight extracted by acid oxalate) plus 2 times the Fe (percnt by weight extracted by acid oxalate) of 5 or more, and 2 times the Fe is more than 8 times the Si. Thus, the mineralogy class is ferrihydritic. Namweon series can be classified as medial, ferrihydritic, thermic family of Pachic Melanudands, not as ashy, thermic family of Typic Melanudands.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.1
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• pp.56-68
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• 2005

We measured nitrate and other nutrients in sediment pore waters retrieved from three sites at the southern upper-tidal flats of the Ganghwa Island. Denitrification rate is estimated by applying a simple 1-D model to the nitrate profiles. Results from Jangwha and Dongmak sites are $7.8{\sim}9.4{\times}10^{-7}{\mu}mol{\cdot}cm^{-2}{\cdot}sec^{-1}$, and $1.4{\sim}3.6{\times}10^{-7}{\mu}mol{\cdot}cm^{-2}{\cdot}sec^{-1}$, respectively. Rates are comparable to those reported around the world in an order of magnitude. Denitrification was lower in summer. The rates were about 1.5 times higher at site where the surface sediments consist of relatively coarser particles. This implies that particle size would control the reactant supply to the subsurface sediment. One may claim the denitrification as an evidence of the biogeochemical purification function of tidal flat. However, the purification seems not a general attribute of a tidal flat when whole system is scrutinized by a thermodynamic criterion. Currently the term 'tidal flat' is used when describing the diverse coastal wetlands such as salt marshes, sandy tidal flats and muddy tidal flats, which exhibit quite different ecological functions. Thus it is worthy of mentioning that the classification of coastal wetlands on the basis of sedimentological characteristics and biogeochemical functions should facilitate our understanding.

• Journal of the Korea Institute of Building Construction
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• v.15 no.4
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• pp.367-373
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• 2015

In this study, fundamental properties of cement were reviewed to apply high fineness cement at low temperature environment. The classified high fineness cement has large proportion of particles below $10{\mu}m$ which affects early hydration: an overall reaction of cement hydration faster. As a result of using high fineness cement, setting time of concrete was reduced and compressive strength was higher than OPC at all ages. Especially, compressive strength was more than double its value compared with OPC after three days curing in low temperature. Faster reaction and higher heat of hydration was verified by calorimetry early and maximum heat of hydration was analyzed by adiabatic temperature raising test. The analysis of this study confirmed that high fineness cement can be suitable to be used in low temperature environment.

• Korean Journal of Soil Science and Fertilizer
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• v.3 no.1
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• pp.61-66
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• 1970

This study examined the morphology and physical and chemical characteristics of the Changpyeong series developed on gently sloping to rolling relief on dissected old paddiplains and terraces. This soil has dark brown silty clay loam A horizons, very thick dark red to red silty clay or clay Bt horizons, and C horizons of old alluvial materials frequently with strongly weathered round cobbles and pebbles. It is strongly acid with a low organic matter content, relatively low in cation exchange capacity, but with relatively high base-status based on amount of extractable cations. There is no obvious changes in particle size distribution with depth and textural B horizons probably have not been formed by podzolization but formed by mechanical movement of clay. This soil is classified as Typic Hapludalfs in USDA 7th approximation and Brunic Luvisols in FAO classification system.