• Journal of the Korean Society of Safety
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• v.27 no.1
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• pp.20-25
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• 2012

The purpose of the study is to assess the extinguishing concentration of inert gases in engine nacelle fire. The experiment was performed with a two dimensional rectangular bluff body stabilized flames, where the fuel was ejected to counter flow and co-flow against an oxidizer stream. Two inert gases, $CO_2$ and $N_2$, were used for extinguishing agent in the oxidizer and methane was used for fuel. The main experimental parameters were the direction of injecting fuel, the kinds of agent and the velocity ratio between air and fuel streams, which controlled the mixing characteristic near bluff body and the strength of recirculation zone in the downstream. The result shows the flame structure and the mode were strongly dependent with fuel/air ratio and the fuel jet direction. For both flow configurations, the extinguishing concentration of $CO_2$ was smaller than the $N_2$ because of the large heat capacity of $CO_2$. However, the concentration of inert gasesat blowout was much smaller than those in the cup burner and coflow jet diffusion flames, which implies that the extinction mechanism of bluff body stabilized flames was mainly due to the aerodynamic aspect. Compared to co-flow fuel injection, the extinguishing concentration of inert gases under counter flow configuration was lower. The effect of direction might result from the mixing characteristic and strength of recirculation zonearound a bluff body. More details should be investigated for the characteristic of recirculation zone in the wake of bluff body using the LES(Large Eddy Simulation).

• YAKHAK HOEJI
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• v.49 no.4
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• pp.275-283
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• 2005

The purpose of the present study was to kinetically investigate the carrier-mediated uptake in the hepatic transport of organic anions, and to simulate the 'in vivo counter-transport' phenomena, using kinetic model which was developed in this study. The condition that the mobility of carrier-ligand complex is greater than that of free carrier is not essential for the occurrence of 'counter-transport' phenomenon. To examine the inhibitory effects on the initial uptake of organic anions by the liver, it is necessary to judge whether the true counter-transport mechanism (trans-stimulation) is working or not. Effects of bromophenol blue (BPB) or bromosulfophthalein (BSP) on the plasma disappearance curves of a 1-anilino-8-naphthalene sulfonate (ANS) were then kinetically analyzed based on a flow model, in which the ligand is eliminated only from the peripheral compartment (liver compartment). Moreover, 'in vivo counter-transport' phenomena were simulated based on the perfusion model which incorporated the carrier-mediated transport and the saturable intracellular binding. The 'in vivo counter-transport' phenomena in the hepatic transport of a organic anions were well demonstrated by incorporating the carrier-mediated process. However, the 'in vivo counter-transport' phenomena may be also explained by the enhancement of back diffusion due to the displacement of intracellular binding. In conclusion, one should be more cautious in interpreting data obtained from so-called 'in vivo counter-transport' experiments.

• Korean Journal of Materials Research
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• v.26 no.10
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• pp.549-555
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• 2016

We have investigated a glass-forming region of $V_2O_5-P_2O_5-ZnO$ glass and the effects of the addition of modifier oxides ($B_2O_3$) to the glass systems as a sealing material to improve the adhesion between the glass frits and a soda lime substrate. Thermal properties and coefficient of thermal expansion were measured using a differential scanning calorimetry, a dilatometer and a hot stage microscopy. Structural changes and interfacial reactions between the glass substrate and the glass frit after sintering (at $400^{\circ}C$ for 1 h) were measured by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscope. The results showed that the adhesion strength increases as the content of $B_2O_3$ at 5 mol% increases because of changes in the structural properties. It seems that the glass structures change with $B_2O_3$, and the $Si^{4+}$ ions from the substrate are diffused to the sealing glass. From these results, we could understand the mechanism of strengthening of the adhesion of soda lime silica substrate by ion-diffusion from the substrate to the glass.

• Macromolecular Research
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• v.17 no.12
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• pp.1025-1031
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• 2009

Several kinds of biodegradable hydrogels were prepared via in situ photopolymerization of Pluronic F127/poly($\varepsilon$-caprolactone) macromer and acrylic acid (AA) comonomer in aqueous medium. The swelling kinetics measurements showed that the resultant hydrogels exhibited both thermo- and pH-sensitive behaviors, and that this stimuli-responsiveness underwent a fast reversible process. With increasing pH of the local buffer solutions, the pH sensitivity of the hydrogels was increased, while the temperature sensitivity was decreased. In vitro hydrolytic degradation in the buffer solution (pH 7.4, $37^{\circ}C$), the degradation rate of the hydrogels was greatly improved due to the introduction of the AA comonomer. The in vitro release profiles of bovine serum albumin (BSA) in-situ embedded into the hydrogels were also investigated: the release mechanism of BSA based on the Peppas equation was followed Case II diffusion. Such biodegradable dual-sensitive hydrogel materials may have more advantages as a potentially interesting platform for smart drug delivery carriers and tissue engineering scaffolds.

• Korean Journal of Materials Research
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• v.14 no.10
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• pp.688-695
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• 2004

The capacitor contact barrier(CCB) layers have been introduced in the FeRAM integration to prevent the Pt/Al reaction during the back-end processes. Therefore, the interdiffusion and intermetallic formation in $Pt(1500{\AA})/Al(3000{\AA})$ film stacks were investigated over the annealing temperature range of $100\sim500^{\circ}C$. The interdiffusion in Pt/Al interface started at $300^{\circ}C$ and the stack was completlely intermixed after annealing over $400^{\circ}C$ in nitrogen ambient for 1 hour. Both XRD and SBM analyses revealed that the Pt/Al interdiffusion formed a single phase of $RtAl_2$ intermetallic compound. On the other hand, in the presence of TiN($1000{\AA}$) barrier layer at the Pt/Al interface, the intermetallic formation was completely suppressed even after the annealing at $500^{\circ}C$. These were in good agreement with the predicted effect of the TiN diffusion barrier layer. But the conventional TiN CCB layer could not perfectly block the Pt/Al reaction during the back-end processes of the FeRAM integration with the maximum annealing temperature of $420^{\circ}C$. The difference in the TiN barrier properties could be explained by the voids generated on the Pt electrode surface during the integration. The voids were acted as the starting point of the Pt/Al reaction in real FeRAM structure.

• Journal of the Korean Ceramic Society
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• v.31 no.11
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• pp.1249-1258
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• 1994

Titanium carbide was synthesized by reacting the prepared titanium powder and carbon black using SHS method sustains the reaction spontaneously, utilizing heat generated by the exothermic reaction itself. In this process, the effect of the particle size of titanium powder on combustion temperature and combustion wave velocity was investigated. By controlling combustion temperature and combustion wave velocity via mixing Ti and C powder with TiC, the reaction kinetics of TiC formation by SHS method was considered. Without reference to the change of combustion temperature and combustion wave velocity, TiC was easily synthesized by combustion reaction. As the particle size of titanium powder was bigger, or, as the amount of added diluent(TiC) increased, combustion temperature and combustion wave velocity were found to be decreased. The formation of TiC by combustion reaction in the Ti-C system seems to occur via two different mechanisms. At the beginning of the reaction, when the combustion temperatures were higher than 2551 K, the reaction was considered to be controlled by the rate of dissolution of carbon into a titanium melt with an apparent activation energy of 148 kJ/mol. For combustion temperatures less than 2551 K, it was considered to be controlled by the atomic diffusion rate of carbon through a TiC layer with an apparent activation energy of 355 kJ/mol. The average particle size of the synthesized titanium carbide was smaller than that of the starting material(Ti).

• KSBB Journal
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• v.28 no.5
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• pp.319-326
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• 2013

This study was carried out to investigate the in vitro and in vivo moisturizing properties and percutaneous absorption of PEG-impregnated Aloe vera gel. The PEG-i-Aloe gel was obtained from dewatering and impregnation by soaking (DIS) of Aloe vera leaf slice. The moisturizing property of the obtained sample was evaluated by moisture determination using gravimetric method in desiccator under different RH% and by water sorption-desorption test on human skin. The transdermal penetration characteristics of PEG-i-Aloe gel was investigated by Franz diffusion cell in vitro transdermal absorption method. PEG-i-Aloe gel had high moisture retention ability and could significantly lead the enhancing skin hydration status as well as reducing the skin water loss due to the film formation as a skin barrier. The skin penetration rate of PEGi- Aloe gel at steady state was 9.76 ${\mu}g/(h{\cdot}cm^2)$ and the quantity of the transdermal absorption was 144 ${\mu}g/cm^2$ in 9 hr. The penetration mechanism was well fitted with Higuchi model ($R^2$ = 0.974-0.994). The results show that PEG-i-Aloe gel has the significant moisturizing effect and strong penetration of the animal skin. It could be used as the moisturizing additive in cosmetic skin products.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.412-412
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• 2008

ENIG(Electroless Nickel Immersion Gold)is a surface treatment method that is used most widely at fine pitch's SMT and BGA packaging process. ENIG has good diffusion barrier of Ni against solder and good wettability due to Au finish. But when the discoloration occurred on the Au finish of ENIG, some key characteristics related to the quality and reliability of PCB such as bondability, solderability and electrical flowing of packaging process could be deteriorated. In this paper, we have performed the water dip test ($88^{\circ}C$ purified water) which accelerates the galvanic corrosion of Ni diffused from the Ni-P layer. That is, the excessive oxidation of the Ni layer could result in non-wetting of the solder because the flux may not be able to remove excessive oxides. Though Au discoloration have been reported to be caused by Ni oxides in many literature, it is still open to verify and discuss The microstructures and chemical compositions have been investigated using FE-SEM, TEM, FIB, EDS and XPS. As a result, authors have found that the Au discoloration in ENIG type is severely caused by the oxidation of the Ni and the mechanism of Au discoloration can be confirmed through the experiment result of water dip test.

• Composites Research
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• v.12 no.6
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• pp.22-30
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• 1999

Since the surface diffusion processed $Nb_3Sn$ superconducting tape has the advantage of having large overall critical current density. it is used for the construction of open type MRI superconducting magnets. However one of the disadvantages of this tape is that $Nb_3Sn$ compound often exhibited multiple cracking due to its intrinsic brittleness when subjected to mechanical loading such as bending and winding during the fabrication process for superconducting coil. This will eventually cause the severe degradation of critical current density. Therefore it is important to understand the microscopic deformation behavior of this kind of superconducting tape under the mechanical loading.In this study, acoustic emission(AE) was used to clarify microscopic deformation behavior at room temperature for $Nb_3Sn$ superconducting tape which was strengthened and stabilized with copper. For this purpose, special attention was paid to AE characteristics including AE event, energy, and amplitude distribution which were associated with microscopic mechanism of deformation of $Nb_3Sn$ superconducting tape under tensile load.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1317-1323
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• 2002

This paper describes the comparison of calculated effective stress with experimental one in austenitic heat resistant steels, STS310J1TB and STS310S with and without a small amount of Nb and N. Based on a solute atoms diffusion model, contribution from soluble nitrogen to the high-temperature strength was numerically examined for austenitic heat-resisting Fe-Cr-Ni-N(STS310J1TB) and Fe-Cr-Ni (STS310S) alloys. The solute atmosphere dragging stress of dislocation was calculated in optional dislocation velocity of STS310J1TB and STS310S at $650^{\circ}C$, $675^{\circ}C$ and $700^{\circ}C$. As a result of the numerical calculation, the solute atmosphere dragging stress of STS310J1TB was about 50 times larger than that of STS310S. When the temperature became high, the maximum value of solute atmosphere dragging stress was small and the velocity of moving dislocation was fast. From the relationship between the dislocation rate and the solute atmosphere dragging stress, the relation of both was proportional and the inclination is about 1 in the level with low velocity of moving dislocation. From above results, the mechanism of dislocation movement in STS310J1TB was the solute atmosphere dragging stress. The solute atmosphere dragging stress, which was calculated from the numerical calculation was close to the effect stress in stress relaxation tests.