• Corrosion Science and Technology
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• v.6 no.4
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• pp.147-153
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• 2007

This study sought to investigate the reaction of Co-binder containing tungsten with molten zinc. Four kinds of Co-W alloys (pure, 10%W, 20%W, 30%W) were prepared using the powder metallurgy method. The specimens were immersion-tested in molten pure zinc baths at $460^{\circ}C$. To evaluate the corrosion property in molten zinc, the weight loss of the specimen was measured after the immersion tests at different immersion times (10~300 min.). Co-10%W alloys, compared with pure cobalt, showed no effect of tungsten addition on the reaction rate in molten zinc. The relationship between the weight loss and the square root of immersion period represents a straight line in both pure cobalt and Co-10%W alloy. The Co-Zn reaction layer in Co- 1O%W alloy consists of $\gamma2$, $\gamma1$, $\gamma$ and ($\beta1$ phases. The rate of weight loss significantly increases and the weight loss behavior is not well accord with the linear relationship as the tungsten content in the Co-W alloy increases. The $\beta1$ layer was not formed on the Co-20%W alloy and neither was a stable Co-Zn intermetallic compound layer found on the Co-30%W alloy. The main cause of increase in reaction rate with increasing tungsten content is related with the instability of the Co-Zn reaction phases as seen on micro-structural analysis.

• Korean Journal of Materials Research
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• v.22 no.4
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• pp.169-173
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• 2012

Recently, various attempts to produce a heat sink made of Al 6xxx alloys have been carried out using die-casting. In order to apply die-casting, the Al alloys should be verified for die-soldering ability with die steel. It is generally well known that both Fe and Mn contents have effects on decreasing die soldering, especially with aluminum alloys containing substantial amounts of Si. However, die soldering has not been widely studied for the low Si aluminum (1.0~2.0wt%) alloys. Therefore, in this study, an investigation was performed to consider how the soldering phenomena were affected by Fe and Mn contents in low Si aluminum alloys. Each aluminum alloy was melted and held at $680^{\circ}C$. Then, STD61 substrate was dipped for 2 hr in the melt. The specimens, which were air cooled, were observed using a scanning electron microscope and were line analyzed by an electron probe micro analyzer. The SEM results of the dipping soldering test showed an Al-Fe inter-metallic layer in the microstructure. With increasing Fe content up to 0.35%, the Al-Fe inter-metallic layer became thicker. In Al-1.0%Si alloy, the additional content of Mn also increased the thickness of the inter-metallic layer compared to that in the alloy without Mn. In addition, EPMA analysis showed that Al-Fe inter-metallic compounds such as $Al_2Fe$, $Al_3Fe$, and $Al_5Fe_2$ formed in the die soldering layers.

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.6
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• pp.865-871
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• 2016

The objective of this study was to investigate the effects of canola and flaxseed oils on the physicochemical properties and sensory quality of emulsion-type sausage made from spent layer meat. Three types of sausage were manufactured with different fat sources: 20% pork back fat (CON), 20% canola oil (CA) and 20% flaxseed oil (FL). The pH value of the CA was significantly higher than the others (p<0.05). The highest water holding capacity was also presented for CA; in other words, CA demonstrated a significantly lower water loss value among the treatments (p<0.05). CA had the highest lightness value (p<0.05). However, FL showed the highest yellowness value (p<0.05) because of its own high-density yellow color. The texture profile of the treatments manufactured with vegetable oils showed higher values than for the CON (p<0.05); furthermore, CA had the highest texture profile values (p<0.05) among the treatments. The replacement of pork back fat with canola and flaxseed oils in sausages significantly increased the omega-3 fatty acid content (p<0.05) over 15 to 86 times, respectively. All emulsion sausages containing vegetable oil exhibited significantly lower values for saturated fatty acid content and the omega-6 to omega-3 ratios compared to CON (p<0.05). The results show that using canola or flaxseed oils as a pork fat replacer has a high potential to produce healthier products, and notably, the use of canola oil produced characteristics of great emulsion stability and sensory quality.

• Korean Journal of Materials Research
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• v.28 no.6
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• pp.361-364
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• 2018

Binary Ti-Al alloys below 51.0 mass%Al content exhibit a breakaway, transferring from parabolic to linear rate law. The second $Al_2O_3$ layer might have some protectiveness before breakaway. Ti-63.1 mass%Al oxidized at 1173 K under parabolic law. Breakaway oxidation is observed in every alloy, except for Ti-63.1 mass%Al. After breakaway, oxidation rates of the binary TiAl alloys below 34.5 mass%Al obey almost linear kinetics. The corrosion rate of Ti-63.1 mass%Al appears to be almost parabolic. As content greater than 63.0 mass% is found to be necessary to form a protective alumina film. Addition of Mo improves the oxidation resistance dramatically. No breakaway is observed at 1123 K, and breakaway is delayed by Mo addition at 1173 K. At 1123 K, no breakaway, but a parabolic increase in mass gain, are observed in the Mo-added TiAl alloys. The binary Ti-34.5 mass%Al exhibits a transfer from parabolic to linear kinetics. At 1173 K, the binary alloys show vary fast linear oxidation and even the Mo-added alloys exhibit breakaway oxidation. The 2.0 mass%Mo-added TiAl exhibits a slope between linear and parabolic. At values of 4.0 and 6.0 mass% added TiAl alloys, slightly larger rates are observed than those for the parabolic rate law, even after breakaway. On those alloys, the second $Al_2O_3$ layer appears to be persistently continuous. Oxidation resistance is considerably degraded by the addition of Mn. Mn appears to have the effect of breaking the continuity of the second $Al_2O_3$ layer.

• Journal of the Korean Ceramic Society
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• v.41 no.4
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• pp.328-333
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• 2004

Hydroxyapatite (HAp) and HAp-Ag composite layers were coated on ZrO$_2$and Si wafer substrates by RF magnetron sputtering technique. The thickness of coating layers was in the range of 0.7∼1.0$\mu\textrm{m}$ and its roughness was 3∼4nm. The heat treated HAp coating layers were composed with nano-sized crystallines. However, the HAp-Ag composite layers showed the mixed structure with crystalline and amorphous phases. The Ca/P ratio of the as-received HAp coating layer was 1.9, but, the value was decreased as the Ag content with increased. Also, the Vickers hardness of HAp coating layer decreased as the Ag content increase.

• Korean Journal of Poultry Science
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• v.27 no.3
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• pp.243-254
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• 2000

The effect of supplemental microbial phytase and non - phytate phosphorus(NPP) levels on layer productivity and nutrient digestibility were conducted in 640 21 weeks - old HyLine brown layer for 12 weeks. Supplemented phytase levels were 0, 300, 500 and 1,000 DPU/kg diet. NPP levels were adjusted with tricalcium phosphate(TCP), which were 0(0.11% NPP), 0.5(0.20), 1.0(0.29) and 1.5%(0.38). ME, CP and Ca levels were maintained at 2,800㎉/kg diet, 16% and 3.5%, respectively. Egg production was increased with phytase compared to without phytase(P〈0.05). Increasement of egg production was higher latter of experimental period. Egg production was not different to phytase levels. Egg production in TCP levels were increased in above 0.5% compared to 0% TCP. Difference of egg production by TCP was higher after 6 week. Especially, egg production to supplemental phytase was higher in 0% TCP. Egg weight was not different to phytase and TCP levels. Egg mass was increased with phytase compared to without phytase, but not difference significantly. There was similar to phytase levels. Egg mass in TCP group was increased in TCP supplementation(P〈0.05). Feed intake was not different in phytase levels, and greater with increasing TCP levels(P〈0.05). Feed conversion was improved with phytase(P〈0.05), and not difference in TCP levels. All of nutrients digestibility tended to improve with phytase, P(P〈0.05), especially. There were not different among phytase levels. The effect of adding phytase was higher in low phosphorus diets compared normal levels. Eggshell breaking strength and eggshell thickness also improved in added phytase(P〈0.05). Tibial ash and P content were slightly increased with phytase, and Ca content also was higher(P〈0.05) compared without phytase. We concluded that supplemental phytase in low phosphorus diet was showed to increase laying performance, feed efficiency, nutrients digestibility, egg quality, and bone development. Phytase supplementation was able to compensate for low NPP diet. We also thought optimum phytase level is 300 DPU, and can decrease NPP supplementation adding phytase in later diet.

• KIPS Transactions on Computer and Communication Systems
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• v.1 no.1
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• pp.29-34
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• 2012

Wireless multicast service can be used for video streaming service to save the network resources by sending the same popular multimedia contents to a group of users at once. For better multimedia streaming multicast service, we propose a quality-aware rate adaptation (QARA) scheme for scalable video multicast in rate adaptive wireless networks. In QARA, transmission rate is determined depending on the content's type and users' channel conditions. First, the base layer is transmitted by a low rate for high reliability. That means we provide basic service quality to all users. On the contrary, the transmission rate for enhancement layer is adapted by using channel condition feedback from a randomly selected node. So, the enhancement layer frames in a multimedia content is sent with various transmission rates. Therefore, each node can be provided with differentiated quality services. Consequently, QARA is capable of serving heterogeneous population of mobile nodes. Moreover, it can utilize network resources more efficiently. Our simulation results show that QARA outperforms utilization of the available transmission rate and reduces the data transmission time.

• Journal of the Korean Magnetics Society
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• v.8 no.6
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• pp.369-373
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• 1998

The exchange anisotropy between NiO antiferromagnetic layer and NiFe ferromagnetic layer has been investigated in NiFe(10 nm)/NiO(60 nm) formed by magnetron sputtering. The NiO films were sputtered from nickel oxide using R. F. poser and NiFe, Ta were deposited using D. C. power under Ar atmosphere. Above all. we studied the exchange anisotropy of Ni-Fe/NiO bilayer, and focused especially on the effect of NiO depostion condition. Our experimental data showed that the dominant factor for determining the exchange anisotropy properties was the Ar pressure during NiO deposition. The better exchange anisotropy properties were found when the NiO film was deposited at low Ar pressure probably due to the flatten interface and the epitaxial tendency of NiO grains and NiFe grains. However, as Ar pressure increased, interfacial diffusion at NiFe/NiO interface and oxygen content of NiO film increase, and consequently reduced the exchange anisotropy. We concluded that the flatten interface and relatively low oxygen content of NiO layer are dominant factors for the enhancement of the exchange anisotropy in NiFe/NiO bilayer.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.2
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• pp.255-266
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• 2022

Messenger applications applied end-to-end encryption on their own to prevent message exposure to servers. Standardization of a group messaging protocol called Message Layer Security (MLS) with end-to-end encryption is being discussed for secure and efficient message communication. This paper performs safety checks based on the operation process and security requirements of MLS. Confidentiality to a middleman server, which is an essential security requirement in messenger communication, can be easily violated by a server administrator. We define a server administrator who is curious about the group's communication content as a curious admin and present an attack in which the admin obtains a group key from MLS. Reminds messenger application users that the server can view your communication content at any time. We discuss ways to authenticate between users without going through the server to prevent curious admin attacks.

• Journal of Korean Society of Forest Science
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• v.87 no.1
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• pp.62-73
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• 1998

This research was conducted to analyze the influence of the environmental factors on water quality such as contents of cation($K^+$, $Na^+$, $Ca^{2+}$, $Mg^{2+}$) and anion($Cl^-$, $NO{_3}^-$, $SO{_4}^{2-}$) in rainfall, throughfall, soil water(A and B layer), and stream water at a small forested watershed. Rainfall, throughfall, soil water(A and B layer), and stream water were sampled at the study sites in Kwanak Arboretum, Seoul National University, in Mt. Kwanak for 14 months(Jul. 1, 1996~Aug. 31, 1997). $Cl^-$ content of stream water correlated with that of soil water tire than that of rainfall and throughfall. Also $NO{_3}^-$ content in soil water was correlated with that of rainfall. Cation($K^+$, $Na^+$, $Ca^{2+}$, $Mg^{2+}$) contents in soil water at layer A and B were significantly correlated with anion($Cl^-$, $NO{_3}^-$, $SO{_4}^{2-}$) of that. The ratio of the average content of $NO{_3}^-$ to $SO{_4}^{2-}$ in rainfall was 0.66. Accordingly the content of $SO{_4}^{2-}$ was higher than $NO{_3}^-$ in rainfall. The amount of anion in stream water was significantly correlated with that in rainfall, throughfall, and soil water. Average content of cation and anion in hydrological processes were decreasing in the following order, soil water(B layer> A layer) > throughfall(Pinus rigida > Prunus serrulata var. spontanea > Carpinus laxiflora) > stream water > rainfall.