• Korean Journal of Materials Research
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• v.6 no.11
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• pp.1090-1098
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• 1996

개조한 가스 금속 아아크 용접공정을 이용하여 SiC/AI 금속기 복합재료를 제조하고 그 특성을 조사하였다. AI 모재위에 강화입자의 크기와 부피분율을 변화하여 다양한 SiC/AI 복합재료층을 제조하였고, 만들어진 복합재료층의 특성은 미세조직관찰과 미소경도시험을 통하여 이루어졌다. 복합재료층의 두께는 약 7-8mm로 측정되었고 균일한 강화입자의 분포도를 얻을 수 있었다. 분산입자의 부피분률은 Ar가스의 유량에 의하여 조절하였고 분산입자의 부피분률이 증가하고 크기가 작아짐에 따라 기지의 수지상 응고조직은 더욱 미세화되었다. 복합재료의 부피경도는 분산입자의 부피분률이 감소함에 따라 낮아졌으나 입자 크기에는 크게 변화가 없는 것으로 나타났다.

• Membrane Journal
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• v.19 no.1
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• pp.25-33
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• 2009

PES (polyethersulfone) membranes with highly enhanced their asymmetry were prepared by phase inversion process. The membranes were prepared by using PES/DMF (N,N-dimethylformamide)/TSA (p-toluenesulfonic acid)/PVP (polyvinylpyrrolidone) casting solution and water coagulant. The pre-coagulation of membrane surface which was induced by an addition of TSA as a demixing agent and PVP as a swelling polymer in the PES solution and humid exposure time, played a crucial role in determining morphological properties and the PWP (pure water permeation) performance. The PES solution was coated on polyester film under condition of 80% humidity for a while ($72{\sim}144$ sec) before immersing in a coagulation bath. The characterization of membranes was carried out by a capillary flow porometer, a FE-SEM and a permeation test apparatus. As the thickness of the smallest pore size layer (SPL) decreased, the asymmetry of membrane increased under conditions of 20 wt% of TSA and 10 wt% of PVP in 11 wt% of PES solution during longer humid contact time. As a result, the membranes showed a remarkable increase of PWP.

• Journal of Veterinary Clinics
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• v.31 no.2
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• pp.85-89
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• 2014

Arterial thromboembolism (ATE) is a common and fatal complication of hypertrophic cardiomyopathy (HCM) in cats. Therefore in this study, we evaluated the hypercoagulability (using plasma concentration of D-dimer) in HCM cats with different stage of heart failure and left atrial enlargement and also investigated the any correlation with echocardiographic indices (including left free wall thickness at diastole, interventricular septal thickness at diastole, LA to Ao ratio, heart failure stage, existence of systolic anterior motion of mitral valve). The median plasma D-dimer concentration in this study population was $0.51{\pm}0.70$ (range 0 to 2.50) ug/mL in the control group, $1.47{\pm}1.29$ (range 0.3 to 5.79) ug/mL in the HCM group, $1.48{\pm}1.65$ (range 0.3 to 5.79) ug/mL in the ISACHC I group, $1.62{\pm}0.4$ (range 1.31 to 2.07) ug/mL in the ISACHC II group, $1.36{\pm}0.91$ (range 0.3 to 2.31) ug/mL in the ISACHC III group, $1.90{\pm}1.60$ (range 0.3 to 5.79) ug/mL in the cat with LA dilation, $1.72{\pm}0.72$ (range 0.6 to 2.31) ug/mL in cats with SEC-T, $1.19{\pm}0.70$ (range 0.3 to 2.31) ug/mL in the cats with SAM, and $1.63{\pm}0.80$ (range 0.6 to 2.31) ug/mL in the cats with ATE. Our study found the median and mean concentration of plasma D-dimer was higher in cat with HCM, ATE, SECT and SAM and clearly provides evidence of hypercoagulability in cats with HCM, although the severity was not correlated to the dilation of LA and the presence of heart failure. This is the first study evaluating the hypercoagulability in cats with HCM in Korea.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.2
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• pp.120-125
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• 2006

By employing a rapid solidification method and atmospheric annealing at $450^{\circ}C-1hr$, we were able to manufacture inexpensively granular CuCo alloy ribbons with thickness of $20{\mu}m$ showing giant magnetoresistance (GMR) ratio of more than 5% at a high magnetic field of 0.5T. To verify maximum MR effect, the MR ratio, saturation magnetization, and microstructure change were investigated with Co contents between 5 and 30 at%. It was possible to obtain GMR ratios of 5.2% at 1.2T, and 3% at 0.5T, which implies an appropriate MR for industrial purpose at a Co content of $8{\sim}l4%$. MR ratio was reduced rapidly at a Co content below 5% due to superparamagnetic effect and at a Co content above 20% due to agglomeration of Co clusters. Surface oxidation during rapid solidification and atmospheric annealing did not have much affect on MR ratio. Our result implies that our economic CuCo granular alloy ribbons may be appropriate for high magnetic field sensor applications with wide content range of $8{\sim}14$ at%Co.

• Membrane Journal
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• v.17 no.1
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• pp.14-22
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• 2007

This is the research about the concentration of trace Magnolia flavor components in water by pervaporation. We have investigated the change of selectivity depending on support membrane structure and active layer thickness using prepared PVDF/PDMS composite membrane. Through the pure water flux test for PVDF support membrane, we could indirectly confirm that as the coagulation temperature decreases and the polymer concentration increases, the surface porosity and pore diameter decreases. Appling these results to transport mechanism, we could explain the effect of support membrane structure for the composite membrane. The selectivity increases as the thickness of PDMS active layer increases. We could know that there is a limitation to describe the transport on the active layer by Fick's law through these results.

• Korean Journal of Materials Research
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• v.25 no.5
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• pp.226-232
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• 2015

High temperature plasma coating technology has been applied to recover damaged aluminum dies from wear by spraying pure aluminum and alumina powder. However, the coated mixed powder layer composed of aluminum and alumina often undergoes a detachment from the substrate, making the coated substrate die unable to maintain its expected life span. In this study, in order to increase the bonding strength between the substrate and the coating layer, a pure aluminum layer was applied as an intermediate bond layer. In order to prepare the specimen with variable bond coating conditions, the bond coat layers with a various gun speed from 10 cm/sec to 30 cm/sec were prepared with coating cycle variations ranging from three to nine cycles. The specimen with a bond coat layer coated with a gun speed of 20 cm/sec and three coating cycles exhibited ~13MPa of adhesion strength, while the specimen without a bond coat layer showed ~6 MPa of adhesion strength. The adhesion strength with a variation of bond coat layer thickness is discussed in terms of coating parameters.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.13-21
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• 2005

I consider the structure of steady wave system which is admitted by the continuum equations for materials that undergo phase transformations with exothermic chemical reaction. In particular, the dynamic phase front structures between liquid and gas phases, and solid and liquid phases are computationally investigated. Based on the one-dimensional continuum shock structure analysis, the present approach can estimate the nano-width of waves that are present in combustion. For illustration purpose, n-heptane is used in the evaporation and condensation analysis and HMX is used in the melting and freezing analysis of energetic materials of interest. On-going effort includes extension of this idea to include broad range of liquid and solid fuels, such as rocket propellants.

• Membrane Journal
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• v.17 no.4
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• pp.329-337
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• 2007

This is the research about a new method to make the internal separation layer with smallest pore size in polyethersulfone (PES) membrane by adding p-toluenesulfonic acid (TSA) and polyvinylpyrolidone (PVP) to polymeric PES solution. The preparation and morphological characterization of PES sheet membranes containing PVP as a hydrophilic swelling material and TSA as a demixing material were performed. As a result by microflow porometery, the PVP and TSA added PES membranes showed good permeabilities and narrow pore size distributions, comparable to those of the commercial membranes. The concentration of PVP affected the PES characteristics on air permeability and surface structure. The concentration of TSA influenced on pore size distribution but do not affect air permeability. The surface images of FE-SEM shows similar pore size when TSA added or not. However, the cross-section images of FE-SEM show that the TSA added PES membranes have a increase of internal layer thickness with smallest pore size.

• Membrane Journal
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• v.15 no.2
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• pp.157-164
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• 2005

In this study, composite hollow fiber membranes were developed for the recovery of olefin monomers in polyolefin industry off-gases. Polyetherimide (PEI) hollow fiber support membranes were fabricated from spinning solutions containing PEI, NMP and polyethylene glycol (PEG). The influence of dope solution and inner coagulant composition on the permeation properties and structure of hollow fiber supports was examined. PDMS was used as a selective layer and coated on PEI hollow fiber support. The thickness of active layer was controlled by changing coating solution concentration. The permeation properties of hollow fiber supports and composite membranes were characterized with a pure gas permeation test. The optimized composite hollow fiber membrane has $10\;{\mu}m$ selective layer and shows excellent separation performance; the ideal selectivity of olefins over nitrogen is in the following order: 1-butylene (6.4) > propylene (17) > ethylene (97), which selectivity data are similar to the intrinsic olefin/nitrogen selectivities of PDMS. This confirms that the new composite hollow fiber membranes suitable for olefin off-gas recovery has developed successfully.

• Journal of Chest Surgery
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• v.43 no.6
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• pp.602-613
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• 2010

Background: As life expectancy has been increased, the cardiac valve disease has been increased. In past, mechanical valve for valve replacement surgery was used widely, but it has many weaknesses, such as hemorrhage, teratogenic effect caused by warfarin, acute mechanical failure, taking warfarin during life, etc. So, the tissue valve is used widely and researches for durability of tissue valve are in progress. Tissue valves being used are all imported in Korea, and there is a lack of information on its geometry and design. So, we studied the geometry of porcine aortic and pulmonary valve, and tried to suggest theoretical basis for making the aortic and pulmonary valve. Material and Method: We harvested aortic and pulmonary valves of 25 pigs and measured the geometry of valve at fresh and glutaraldehyde (GA) fixed state. In each group, we measured the diameter of the base, diameter of commissure, valve height, commissural height, etc. Also, for making implantable porcine and bovine pericardial valve, we designed the valve stent form, thickness, height, and leaflet size, form, thickness by different size of valve. Result: The aortic and pulmonary valve geometry and ratio were measured in each group. The right coronary cusp of aortic valve and right facing cusp of pulmonary valve was bigger than other cusps and non coronary cusp was smaller than others (RCC: NCC : LCC=1 : 0.88 : 1). Valve height was correlated to the leaflet size. We designed the outer diameter of stented porcine aortic valve from 19 mm to 33 mm and designed stent height and width, using previous measured ratio of each structure, stent thickness, working thickness (for making valve). Also, we designed the size of stent and form for stented bovine pericardial valve, considering diameter of valve, leaflet length, height and leaflet minimum coaptation area. Conclusion: By measuring of 25 pig's aortic and pulmonary valve geometry and ratio, we can make theoretical basis for making implantable stented porcine valve and bovine pericardial valve in various size. After making implantable valve using these data, it is necessary to do in vivo and in vitro researches, furthermore.