• Transactions of Materials Processing
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• v.33 no.3
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• pp.178-184
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• 2024

In this study, we investigated the effects of extrusion ratio and extrusion temperature on the microstructure and tensile properties of extruded Mg-6Al-0.3Mn-0.3Ca-0.2Y (SEN6) alloy. As the extrusion ratio and temperature increase, dynamic recrystallization during extrusion is promoted, leading to the formation of a fully recrystallized microstructure with increased grain size. Additionally, the increases in extrusion ratio and temperature lead to texture strengthening, exhibiting a higher maximum texture intensity. The extruded materials contain three types of secondary phases, i.e., Al₈Mn₄Y, Al₂Y, and Al₂Ca, with irregular or polygonal shapes. The quantity, size, distribution, and area fraction of the second-phase particles are nearly identical between the two materials. Despite its larger grain size, the tensile yield strength of the material extruded at 450 ℃ and an extrusion ratio of 25 (450-25) is higher than that of the material extruded at 325 ℃ and an extrusion ratio of 10 (325-10), which is mainly attributed to the stronger texture hardening effect of the former. The ultimate tensile strength is similar in the two materials, owing to the higher work hardening rate in the 325-10 extrudate. Despite differences in grain size and recrystallization fraction, numerous twins are formed throughout the specimen during tensile deformation in both materials; consequently, the two materials exhibit nearly the same tensile elongation.

• KSBB Journal
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• v.19 no.3
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• pp.169-173
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• 2004

The Rhodiola Sachalinensis 5 g were mixed and extracted with methanol 150 $m\ell$ at the room temperature for 12 h. The effluents were collected and grouped into the two. Un this experimental condition, the mobile phase composition were linearly changed as follows; water/methanol : 90/10 - 30/70 (vol. %, for 5 min), 30/70 - 10/90 (vol. %, for 15 min) and an analytical column (3.9 ${\times}$ 25 em, 15 $\mu\textrm{m}$ particle size, and 300 ${\AA}$ pore size) was utilized. The performance of the extracted Rhodiola Sachalinensis as a whitening agent was not favorable, so it classifies the Rhodiola Sachalinensis extractions with two fractions and collects each fraction for whitening agent assay. For the in-vivo melanin production ratio assay that used melanin-a cell in 10 ppm concentration, it was 58.6%, the first fraction of the effluents collected between 1.0 and 4.0 min, while it was 60％ between 10.4 and 17.6 min for the second fraction, which were more efficient than that of arbutin, 45.6%.

• Food Science of Animal Resources
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• v.37 no.1
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• pp.18-28
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• 2017

Pastirma is a dry-cured meat product, produced from whole beef or water buffalo muscles. This study was carried out to investigate the effect of production stages (raw meat, after curing, after $2^{nd}$ drying and pastirma) on the total lipid, neutral lipid, phospholipid and fatty acid composition of phospholipid fraction of pastirma produced from beef M. Longissimus dorsi muscles. The pH and colour ($L^*$, $a^*$ and $b^*$) analyses were also performed in raw meat and pastirma. It was found that pastirma production stages had significant effects (p<0.01) on the total amounts of lipid, neutral lipid and phospholipid, and the highest amounts of lipid, neutral lipid and phospholipid were detected in pastirma. In pastirma, neutral lipid ratio was determined as $79.33{\pm}2.06%$ and phospholipid ratio as $20.67{\pm}2.06%$. Phospholipids was proportionately lower in pastirma than raw meat. Pastirma production stages affected pentadecanoic acid (15:1) (p<0.01), linoleic acid (18:2n-6) (p<0.05), ${\gamma}-linoleic$ acid (18:3n-6) (p<0.05), erucic acid (22:1n-9) (p<0.05), docosapentaenoic acid (22:5n-6) (p<0.05), total unsaturated fatty acid (${\Sigma}USFA$) (p<0.05) and total saturated fatty acid (${\Sigma}SFA$) (p<0.05) ratios of phospholipid fraction and also the moisture content (p<0.01). Pastirma process also affected pH and colour ($L^*$, $a^*$ and $b^*$) values (p<0.01), and these values were higher in pastirma than raw meat.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.8 s.227
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• pp.968-975
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• 2004

Nanofluids have anomalously high thermal conductivities at very low fraction, strongly temperature-dependent and size-dependent conductivities, and three-fold higher critical heat flux than that of base fluids. Traditional conductivity theories such as the Maxwell or other macroscale approaches cannot explain why nanofluids have these intriguing features. So in this paper, we devise a theoretical model that accounts for the fundamental role of dynamic nanoparticles in nanofluids. The proposed model not only captures the concentration and temperature-dependent conductivity, but also predicts strongly size-dependent conductivity. Furthermore, we physically explain the new phenomena for nanofluids. In addition, based on a proposed model, the effects of various parameters such as the ratio of thermal conductivity of nanofluids to that of a base fluid, volume fraction, nanoparticle size, and temperature on the thermal conductivities of nanofluids are investigated.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1388-1393
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• 2004

Investigators have been perplexed with the thermal phenomena behind the recently discovered nanofluids, fluids with unprecedented stability of suspended nanoparticles although huge difference in the density of nanoparticles and fluid. For example, nanofluids have anomalously high thermal conductivities at very low fraction, strongly temperature-dependent and size-dependent conductivities, and three-fold higher critical heat flux than that of base fluids. Traditional conductivity theories such as the Maxwell or other macroscale approaches cannot explain why nanofluids have these intriguing features. So in this paper, we devise a theoretical model that accounts for the fundamental role of dynamic nanoparticles in nanofluids. The proposed model not only captures the concentration and temperature-dependent conductivity, but also predicts strongly size-dependent conductivity. Furthermore, we physically explain the new phenomena for nanofluids. In addition, based on a proposed model, the effects of various parameters such as the ratio of thermal conductivity of nanofluids to that of a base fluid, volume fraction, nanoparticle size, and temperature on the thermal conductivities of nanofluids are investigated.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.5
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• pp.724-732
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• 2021

This study used response surface methodology to investigate the optimal conditions to reduce the bitterness of alcalase-treated anchovy hydrolysate (AAH) by the aminopeptidase active fraction (AAF) derived from the common squid Todarodes pacificus hepatopancreas. The central composite design selected AAF/AAH ratio (X₁, %) and hydrolysis time (X₂, h) as independent variables, and the degree of hydrolysis (Y₁) and bitterness (Y₂) as dependent variables. The uncoded values of the multiple response optimization for independent variables were 3.4% for the AAF/AAH ratio and 9.2 h for the hydrolysis time. The predicted values of the yield and bitterness score of alcalase-AAF continuously treated anchovy hydrolysate (AAAH) under the optimized conditions were 68.9% and 4.6 points, respectively. Their measured values of 69.5% for yield and 4.6±0.5 points for bitterness were similar to the predicted values. The food components of AAAH were 91.4% (moisture), 7.5% (protein), 0.1% (lipid) and 0.6% (ash). The findings indicate the potential value for use as an anchovy seasoning base. The results also confirm that the bitterness of AAH was remarkably improved by AAF and implicates AAF derived from squid hepatopancreas as a good enzyme to catalyze reduced bitterness.

• Journal of Korean Society of Water and Wastewater
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• v.14 no.2
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• pp.147-156
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• 2000

In this study, the optimal operation parameters of MLE(Modified Ludzack-Ettinger) process treating the liquid supernatant separated from the slurry excreta of swine feedlot was studied as a promising biological treatment process. The nitrogen removal characteristics with different volume ratio between nitrification and denitrification reactor and the operational effect with different nitrogen loading rate, and different C/N($COD_{Cr}/TKN$) ratio were investigated. Based on the laboratory results, pilot MLE plant was operated to examine the effect of ambient temperature for five months including winter. The denitrification reactor which is 20% of total volume was proposed as the most optimal volume fraction for nitrification and denitrification. The optimum ratios of F/M and $F_N/M$ were increased with increase of the C/N ratio. However, optimum F/M ratio was changed more rapidly than $F_N/M$ ratio with increase of the C/N ratio. Therefore, MLE process is desirable to be controlled by F/M ratio in the range of high C/N ratio and by $F_N/M$ ratio in the range of low C/N ratio. Pilot MLE plant showed the higher removal efficiencies of COD and TKN in winter than in summer and was operated most stably at the temperature of $20{\sim}25^{\circ}C$ for mixed liqour.

• Journal of the Korean Society of Industry Convergence
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• v.18 no.2
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• pp.110-118
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• 2015

In this study, it is designed and used the test engine bed which is installed with turbocharger, and in addition to equipped using by oxygen adder. It has been controlled the oxygen volumetric fraction of intake air chrge, and supercharged flow rate into the cylinder of SI 4-stroke engine, and then, has been analyzed engine performance, combustion characteristics, and exhaust emission as analysis parameters. The tested parameters were the oxygen fraction and the variation of engine speed and air-fuel ratio.

• Korean Journal of Materials Research
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• v.29 no.6
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• pp.349-355
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• 2019

This study deals with the microstructure and tensile properties of 600 MPa-grade seismic reinforced steel bars fabricated by a pilot plant. The steel bar specimens are composed of a fully ferrite-pearlite structure because they were air-cooled after hot-rolling. The volume fraction and interlamellar spacing of the pearlite and the ferrite grain size decrease from the center region to the surface region because the surface region is more rapidly cooled than the center region. The A steel bar specimenwith a relatively high carbon content generally has a higher pearlite volume fraction and interlamellar spacing of pearlite and a finer ferrite grain size because increasing the carbon content promotes the formation of pearlite. As a result, the A steel bar specimen has a higher hardness than the B steel bar in all the regions. The hardness shows a tendency to decrease from the center region to the surface region due to the decreased pearlite volume fraction. On the other hand, the tensile-to-yield strength ratio and the tensile strength of the A steel bar specimen are higher than those of the B steel bar with a relatively low carbon content because a higher pearlite volume fraction enhances work hardening. In addition, the B steel bar specimen has higher uniform and total elongations because a lower pearlite volume fraction facilitates plastic deformation caused by dislocation slip.

• Journal of Life Science
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• v.18 no.6
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• pp.832-838
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• 2008

Mackerel water-soluble protein fraction produced by washing the mackerel meat were concentrated by isoelectric point shifting precipitation process, and the concentrates were utilized as the alternative feed of fish meal. In the 1st aquaculture diet experiment for Israel common carp, the feed conversion ratio decreased in proportion to the rise in the percentage of the recovered protein containing a residual lipid, which was added to the fish meal. It was supposed that the low feed efficiency was because of lipid oxidation in the recovered protein fraction. In addition, 2nd aquaculture diet experiment for Israel common carp was conducted after removing the oxidized lipid in the recovered protein fish meal. When a portion of the fish meal was substituted by the recovered protein devoid of the residual lipid, the feed conversion ratio increased in proportion to the amount of the substitute being added to the fish meal. Therefore, the recovered protein fraction of the mackerel washing wastewater from mackerel processing factory could be used as the alternative feed of fish meal.