• Journal of Powder Materials
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• v.24 no.3
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• pp.202-209
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• 2017

A cold-work tool steel powder is used to fabricate 3-dimensional objects by selective laser melting using a high-pressure gas atomization process. The spherical powder particles form continuous carbide networks among the austenite matrix and its decomposition products. The carbides comprise Nb-rich MC and Mo-rich $M_2C$. In the SLM process, the process parameters such as the laser power (90 W), layer thickness ($25{\mu}m$), and hatch spacing ($80{\mu}m$) are kept fixed, while the scan speed is changed from 50 mm/s to 4000 mm/s. At a low scan speed of 50 mm/s, spherical cavities develop due to over melting, while they are substantially reduced on increasing the speed to 2000 mm/s. The carbide network spacing decreases with increasing speed. At an excessively high speed of 4000 mm/s, long and irregularly shaped cavities are developed due to incomplete melting. The influence of the scan pattern is examined, for which $1{\times}1 mm^2$ blocks constituting a processing layer are irradiated in a random sequence. This island-type pattern exhibits the same effect as that of a low scan speed. Post processing of an object using hot isostatic pressing leads to a great reduction in the porosity but causes coarsening of the microstructure.

• Journal of Powder Materials
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• v.20 no.1
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• pp.53-59
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• 2013

Fe-TiC composite powder was fabricated via two steps. The first step was a high-energy milling of FeO and carbon powders followed by heat treatment for reduction to obtain a (Fe+C) powder mixture. The optimal condition for high-energy milling was 500 rpm for 1h, which had been determined by a series of preliminary experiment. Reduction heat-treatment was carried out at $900^{\circ}C$ for 1h in flowing argon gas atmosphere. Reduced powder mixture was investigated by X-ray Diffraction (XRD), Field Emission-Scanning Electron Microscopy (FE-SEM) and Laser Particle Size Analyser (LPSA). The second step was a high-energy milling of (Fe+C) powder mixture and additional $TiH_2$ powder, and subsequent in-situ synthesis of TiC particulate in Fe matrix through a reaction of carbon and Ti. High-energy milling was carried out at 500 rpm for 1 h. Heat treatment for reaction synthesis was carried out at $1000{\sim}1200^{\circ}C$ for 1 h in flowing argon gas atmosphere. X-ray diffraction (XRD) results of the fabricated Fe-TiC composite powder showed that only TiC and Fe phases exist. Results from FE-SEM observation and Energy-Dispersive X-ray Spectros-copy (EDS) revealed that TiC phase exists uniformly dispersed in the Fe matrix in a form of particulate with a size of submicron.

• Journal of the Korean Society of Food Culture
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• v.25 no.6
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• pp.779-787
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• 2010

The principal objective of this study was to determine the optimal mixing conditions for three amounts of onion powder, sugar, and butter to prepare onion powder cookies. The experimental design was based on the central composite design methodology of response surface, which included 16 experimental points including two replicates for onion powder, sugar, and butter. The mechanical and sensory properties of the cookies were measured, and these values were applied to the mathematical models. A canonical form and perturbation plot showed the influence of each ingredient on the mixed final product. The results of the spread ratio did not show significant results, but hardness increased with increasing quantities of onion powder and sugar but decreased with butter (p<0.01). The color lightness "L" value increased with increasing quantities of sugar and butter but decreased with added onion powder. In contrast, the redness color "a" value increased with increasing quantities of onion powder and sugar. Sugar did not affect the yellowness color "b" value, but the color b value increased with increasing onion powder and sugar. The results of a sensory evaluation using the predicted model showed significant values for flavor (p<0.01), texture (p<0.05), taste (p<0.05), and overall quality (p<0.01). As a result, the optimum formulation by numerical and graphical methods was calculated as 12.58 g onion powder, 35 g sugar, and 52.38 g butter.

• Korean Journal of Materials Research
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• v.24 no.6
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• pp.277-284
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• 2014

Using the spray pyrolysis process, nano-sized cobalt oxide powder with average particle size below 50 nm was prepared from cobalt chloride solution. The influences of the raw material solution on the properties of the powder formed examined. When the concentration of Co was low(20 g/L), the average particle size of the powder formed was roughly 20 nm, and the cohesion between these particles was significantly strong. When the concentration of Co increased to 100 g/L, the droplets nearly failed to exist in circular form and reflected a severely divided form. Furthermore, the average size of the particles formed was roughly 40 nm, and the particles reflected a polygonal form. When the solution was increased to nearly saturation level (Co at 200 g/L), the particle size distribution reflected significant unevenness due to severe droplet division while the surface also reflected significant unevenness. Furthermore, the average size of the particles formed increased significantly to 70 nm. The results of XRD analysis showed that the strength of the peaks reflected very little change when the concentration of Co was increased from 20 g/L to 50 g/L. Alternatively, when the concentration was increased to 100 g/L, the strength of the peaks increased compared to when the concentration was 50 g/L. However, when the concentration was increased to 200 g/L, the strength of the peaks failed to reflect significant change compared to when the concentration was 100 g/L. The specific surface area dramatically decreased by 30 % when the concentration of Co was increased from 20 g/L to 50 g/L. Alternatively, when the concentration of Co the solution increased to 100 g/L, the specific surface area decreased by roughly 15 %. Furthermore, when the concentration of Co was increased to nearly saturation level(200 g/L), the specific surface area decreased by roughly 35%.

• Animal Bioscience
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• v.35 no.2
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• pp.247-259
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• 2022

Objective: This study was conducted to investigate the effects of age and diet forms on growth-development patterns, serum metabolism indicators, and parameters of body fat deposition in Cherry Valley ducks. Methods: According to the hatching age and initial weight, a total of 150 1-day-old male SM3 Cherry Valley ducks were randomly assigned to two diet forms (pellet vs powder form). Each treatment had with 5 replicates per treatment and 15 meat ducks per replicate. The study lasted 42 d, which was divided into two periods (1 to 21 vs 22 to 42 d). Results: Our results showed that compared with powder group, ducks in pellet group had greater growth performance during different period (p<0.05). The inflection point was 24 d and was not numerically affected by diet forms. Increasing age (42 vs 21 d) significantly increased the weight of body fat and hepatic fat metabolism related enzyme activities in ducks (p<0.05), meanwhile, increasing age (42 vs 21 d) improved serum metabolism indicators and decreased mRNA expression levels of fat metabolism-related genes in liver (p<0.05). Ducks fed different diets (pellet vs powder form) increased growth performance as well as the weight of body fat and improved serum metabolism indicators (p<0.05). In addition, interactions were found between age and diet forms on the levels of serum metabolism indicators in ducks (p<0.05). Conclusion: In conclusion, powder feed reduced growth performance of ducks, and the day of inflection point was 24 days old. Ducks with higher age or fed with pellet diet showed higher fat deposition. The effect of age and feed forms on body fat deposition might result from changes in the contents of serum metabolism indicators, key enzyme activity of lipid production, and hepatic gene expressions.

• Food Science of Animal Resources
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• v.35 no.4
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• pp.572-576
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• 2015

The most commonly used infant formulas contain lactose originating from cow milk. Goat milk has recently been claimed to be nutritionally more effective for infants than other milks. In baby foods, much emphasis is placed on the concentrations of intestinal microflora-promoting oligosaccharides, which are generally transferred into lactose from milk during crystallization process. Here we show that higher level of free sialic acid is present in goat lactose powder compared to cow lactose powder. Without proteinase K treatment, the amount of 3-sialyllactose and 6-sialyllactose were similar in goat and cow lactose powders. However, after proteolysis, 6-sialyllactose was present at higher levels in goat than in cow lactose powder. Galactooligosaccharides, a group of prebiotics, are present in milk in the form of glycoproteins. Galactooligosaccharide content was also higher in goat lactose powder than in cow lactose powder.

• Journal of the Korean Dietetic Association
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• v.16 no.4
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• pp.341-352
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• 2010

The aim of this study was to use purple sweet potato powder to develop a recipe for a nutritional cookie with an optimal composition of ingredients and texture, in order to acquire strong preference responses by all age groups in sensory tests. Wheat flour was partially substituted with purple sweet potato powder to reduce the wheat flour content of the cookies. Measurements were made and analyzed according to the Response Surface Methodology technique, which showed 16 experimental points including 3 replicates for the purple sweet potato powder, sugar, and butter. The compositional and functional properties of the sample were measured, and the values obtained were applied to a mathematical model. A canonical form and perturbation plot showed the influence of each ingredient on the final product mixture. The results of sensory evaluations showed very significant values for flavor (P<0.0071), texture (P<0.0306), taste (P<0.0190), and overall quality (P<0.0142). Instrumental analysis showed significant values for hardness (P<0.0027), yellowness (P<0.0061) and spread ratio (P<0.0001). The optimal compositional ratios were determined to be 21.75 g for the purple sweet potato powder, 37.05 g for the sugar, and 60.59 g for the butter.

• Journal of Powder Materials
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• v.16 no.1
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• pp.33-36
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• 2009

In order to increase the magnetic loss for electromagnetic(EM) wave absorption, the soft magnetic $Fe_{73}Si_{16}B_7Nb_3Cu_1$(at%) alloy strip was used as the basic material in this study. The melt-spun strip was pulverized using an attrition mill, and the pulverized flake-shaped powder was crystallized at $540^{\circ}C$ for 1h to obtain the optimum grain size. The Fe-based powder was mixed with 2 wt% $BaTiO_3$, $0.3{\sim}0.6$ wt% carbon black, and polymer-based binders for the improvement of electromagnetic wave absorption properties. The mixture powders were tape-cast and dried to form the absorption sheets. After drying at $100^{\circ}C$ for 1h, the sheets of 0.5 mm in thickness were made by rolling at $60^{\circ}C$, and cut into toroidal shape to measure the absorption properties of samples. The characteristics including permittivity, permeability and power loss were measured using a Network Analyzer(N5230A). Consequently, the properties of electromagnetic wave absorber were improved with the addition of both $BaTiO_3$ and carbon black powder, which was caused by the increased dielectric loss of the additive powders.

• Preventive Nutrition and Food Science
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• v.13 no.4
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• pp.340-347
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• 2008

This study was conducted to develop a recipe for a nutritional cookie with lotus root powder that had the optimal composition of ingredients and texture resulting in high preference by all age groups. Wheat flour was partially substituted with lotus root powder to reduce its content. Response Surface Methodology was used to analyze the measured results, which showed 16 experimental points including 2 replicates for lotus root powder, sugar and butter. The compositional and functional properties were measured, and these values were applied to a mathematical model. A canonical form and perturbation plot showed the influence of each ingredient on the final mixture product. The sensory evaluation results showed significant values in color (p<0.01), texture (p<0.05) and overall quality (p<0.05). As a result, the optimal sensory ratio was determined to be 22.59 g of lotus root powder, and 53.08 g of sugar for every 120 g of butter.

• Preventive Nutrition and Food Science
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• v.4 no.1
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• pp.38-42
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• 1999

Antimutagenic effects of 5 kinds of kochujang(Korean red pepper soybean paste) samples compared with doenjang(Korean soy paste) were studied using the Ames test with Salmonella typhimurium TA100 and the SOS chromotest, with E. Coli PQ37. Th eantimutatenic effects of methanol extracts from red pepper powder and meju(fermented soybean) powder, the major ingredients of the kochujang,were also evaluated for the mutagenicity of aflatoxin B1 (AFB1) in the Ames assay. The methanol extracts from the kochujang samples showed lower antimutagenicities than those of doenjang against AFB1 and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the Ames assay. Traditional kochujang I and II exhibited strong antimutagenic activity against AFB1 and MNNG. The traditional kochujang samples against MNNG were aslo observed in the SOS chromotest system with the same fashions as shown in the Ames mutagenicity test. The methanol extracts from meju powder had the strongest inhibitory effects on mutabenicity induced by AFB1, however, those form red pepper powder showed lower inhibition rate than kochujang. These results suggest that traditional kochujang exhibit higher antimutagenic acitivity than the commercial variety, and that meju powder seems to be one of the major antimutagenic components in kochujang.