• Tunnel and Underground Space
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• v.26 no.3
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• pp.235-252
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• 2016

This study presents a methodology to reproduce the mechanical behavior of isotropic or transversely isotropic rock using the polygonal grain-based distinct element model. A numerical technique to monitor the evolution of micro-cracks during the simulation was developed in the present study, which enabled us to examine the contribution of tensile cracking and shear cracking to the progressive process of the failure. The numerical results demonstrated good agreement with general observations from rock specimens in terms of the behavior and the evolution of micro-cracks, suggesting the capability of the model to represent the mechanical behavior of rock. We also carried out a parametric study as a fundamental work to examine the relationships between the microscopic properties of the constituents and the macroscopic behavior of the model. Depending on the micro-properties, the model exhibited a variety of responses to the external load in terms of the strength and deformation characteristics. In addition, a numerical technique to reproduce the transversely isotropic rock was suggested and applied to Asan gneiss from Korea. The behavior of the numerical model was in good agreement with the results obtained in the laboratory-scale experiments of the rock.

• Tunnel and Underground Space
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• v.24 no.3
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• pp.243-254
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• 2014

The present study introduces a numerical technique to simulate the mechanical behavior of brittle rock, based on a grain-based model combined with Universal Distinct Element Code (GBM-UDEC). Using the technique, the microstructure of rock sample was represented as an assembly of deformable polygonal grains, and the failure process with the evolution of micro tensile cracks under compression was examined. In terms of the characteristics of strength and deformation, the behaviors of the simulated model showed good agreement with the observations in the laboratory-scale experiments of rock.

• Applied Biological Chemistry
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• v.27 no.4
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• pp.245-251
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• 1984

Physicochemical properties of arrowroot starch were investigated. The starch had blue value of 0.397, alkali number of 10.1 and amylose content of 22.0%. The starch was practically insoluble in water up to $55^{\circ}C$. X-ray diffraction was C pattern, but was close to A pattern. The alkali number, X-ray pattern and viscogram of the starch and retrogadation rate of the starch gels indicated that the properties of the arrow root starch were close to those of cereal starches.

• Korean Journal of Materials Research
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• v.6 no.4
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• pp.357-363
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• 1996

다공성 알루미나 지지체를 이용하여 졸에 침지하는 미세한 기공으로 이루어진 티타니아 여과막을 제조하였다. 티타니아 졸은 현\ulcorner액 재안정화 공정으로 제조하였고, pH 1.23-1.32범위에서 졸의 평균입지크기는 15nm 이하였다. 이 여과막은 $600^{\circ}C$에서 1시간 열처리한 경우 평균입도는 30-40nm로서 입도 분포가 좁은 양호한 여과막을 제조하였다. 이때 입자의 모양은 구형이었다. 열처리 온도가 $600^{\circ}C$보다 높아지면 여과막을 구성하는 입자 모양을 다각형으로 변하고 입도의 분포는 넓어졌다.

• Applied Biological Chemistry
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• v.29 no.4
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• pp.333-338
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• 1986

Physicochemical properties of starch isolated from germinated corn were investigated and compared with those of nongerminated corn starch. Amylose content and initial gelatinization temperature of germinated starch were lower than those of nongerminated starch. Swelling power and solubility of both starches exhibited two stage behavior, however germinated starch revealed lower swelling power and higher solubility compared to those of nongerminated starch. Both starches showed a typical A type X-ray diffraction and irregular oval shape including partly polygon with the size of $10-25{\mu}m$. However, germinated starch showed many holes with the size of $1-2{\mu}m$ on the surface of granule.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.4
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• pp.567-572
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• 1997

The ZnO powder was prepared under glycothermal conditions by precipitation from metal nitrates with aqueous potassium hydroxide. The fine powder was obtained at temperatures as low as 225 to $275^{\circ}C$, The microstructure and phase of the powder were studied by SEM and XRD. The properties of the ZnO powder were studied as a function of various parameters (reaction temperature, reaction time, solid loading, etc). The average particle size of the ZnO increased with increasing reaction temperature. After glycothermal treatment at $225^{\circ}C$ for 8 h, the average particle size of the ZnO powder was about 150 nm and the particle size distribution was narrow.

• Conservation Science in Museum
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• v.14
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• pp.61-67
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• 2013

Lacquerware of Goryeo period was variously developed from the early 10th century to the 14th century and became lacquerware inlaid with mother-of-pearl which shows creativity with splendid heyday. For characteristics, splendid and close mother-of-pearl. Characteristic of decoration method is to use gold painting method, Tortoise shell and metal line. Drawing is done with gold dust and gold painting method decorating lacquerware are very splendid from an artistic and decorative aspect, but gold painting is easily lost. So, it's currently difficult to find in relics succeeded. Therefore, there are domestically insufficient studies on gold painting method in Goryeo period, so this researcher intended to observe gold painting of lacquerware excavated in Goryeo period through the microscope, investigate characteristics, mixture, etc. of gold dust and provide data of studies on the recovery of ancient technology. As the result, gold dust particle has various shapes such as irregular square, polygon and triangle under the size from 2 ㎛ to 20 ㎛. The end of gold dust is rolled and overlapped and irregular particle seems to be similar to the shape of crumpled paper. This research showed that gold dust used in gold painting of Goryeo period had used gold dust made by grinding gold leaf to gold painting.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.57 no.1
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• pp.41-50
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• 2012

The study was carried out to analyze the relationship between analysis of antioxidant activity and the level of functional components according to particle size of corn silk. Particle size was classified into 5 groups. By particle size distribution and color difference, the total phenol content and DPPH radical scavenging activity were observed. The particle sizes of corn silk were $199.17{\mu}m$, $178.27{\mu}m$, $85.48{\mu}m$, $27.4{\mu}m$ and $20.97{\mu}m$, respectively. The lightness of colored pigments was increased when the particle size was decreased. The contents of free sugar (fructose, glucose, galactose, sucrose, and maltose) of corn silk were analyzed using a HPLC. The total phenol contents by the particle sizes of corn silk were 2.01 mg/g, 2.02 mg/g, 2.06 mg/g, 2.26 mg/g and 2.26 mg/g, respectively. DPPH radical scavenging activities of samples were 21.00%, 21.75%, 22.90%, 24.35% and 23.67%, respectively. Antioxidative activities of Trolox and Fe(II) in corn silk were measured by ferric reducing antioxidant power (FRAP) assay and Trolox equivalent antioxidant capacity (TEAC) assay. TEAC values of samples were $2.36{\mu}mol$ TE / g dw, $2.81{\mu}mol$ TE / g dw, $3.20{\mu}mol$ TE / g dw, $3.36{\mu}mol$ TE / g dw, and $3.44{\mu}mol$ TE / g dw, respectively. FRAP values of samples were $11.67{\mu}mol$ Fe(II) / g dw, $12.80{\mu}mol$ Fe(II) / g dw, $13.43{\mu}mol$ Fe(II) / g dw, $13.85{\mu}mol$ Fe(II) / g dw and $15.95{\mu}mol$ Fe(II) / g dw, respectively. Total phenolic content and antioxidantive activities based on FRAP assay and TEAC assay were increased with decreasing particle size. In addition, DPPH radical scavenging activity was also increased. A significant correlation was also noted between DPPH radical scavenging activities and the content of phenolic compounds.

• Applied Biological Chemistry
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• v.30 no.2
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• pp.179-185
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• 1987

The physicochemical properties and characteristics of sweet potato starches which were isolated from the six varieties were investigated. The shapes of starch granules which observed through photomicroscope and scanning electron microscope lucre round and polygonal, but those of the Shinmi were most polygonal, and the average diameters were in the range of $10.4{\sim}14.2$ microns. The amylose contents were between 25% and 28%, and blue values and alkali numbers were in the range of $0.29{\sim}0.36$, $7.0{\sim}12$, respectively. The swelling power and solubility patterns of the starches were negligible until $50^{\circ}C$, thereafter it increased rapidly and the Eunmi showed highest water binding capacity of 211.6%. Amylogram pattern of 6% starch solutions were similar to no peak viscosity, but maximum viscosity varied widely with varieties. A significant positive correlation was observed between amylose content and average gelatinization temperature. Taste and texture of the steam cooked sweet potatoes were negatively and positively correlated with moisture and amylose contents, respectively, while those of the microwave cooked sweet potatoes were only positively correlated with amylose contents.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.12
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• pp.1762-1768
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• 2016

The objective of this study was to investigate the physicochemical properties of rice flour at different degrees of milling (DOM) and their influence on cooking, color, textural, and sensory properties of rice noodles. Higher DOM flour resulted in higher value of lightness and lower value of yellowness. Transition temperatures of rice flour were not significant, whereas the enthalpy of gelatinization increased with an increase in milling degree. Rice noodles were prepared with rice flours of DOM, and their quality and sensory properties were investigated. Cooking properties of rice noodles were not affected by DOM; however, color values were affected by DOM. In textural properties, values of hardness and chewiness of rice noodles were significantly reduced with an increase in milling degree. The sensory scores for overall acceptability, appearance, and texture were highest in higher DOM noodles (DOM 10% and DOM 12%).