• Textile Coloration and Finishing
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• v.30 no.2
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• pp.117-129
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• 2018

Cellulose has been widely applied into various medical fields including scaffolding, tissue engineering and tissue formation. In this study, we manufactured cellulose medical fiber from Styela clava tunics(SCT-CS) and analyzed the tensile strength, elongation at break, fluid uptake and surface morphology. And then, the biocompatibility and toxicity of SCT-CS were measured in Sprague-Dawley(SD) rats after the implantation for 30, 60 and 90 days. The level of tensile strength and fluid uptake were lower in SCT-CS than chromic catgut(CCG), while elongation at break level were maintained the higher in SCT-CS. Also, the roughness with pronounced surface patterns as a result of in vivo degradation was significantly greater in CCG than this of SCT-CS although these levels gradually appeared with time in both groups. After implantation for 90 days, SCT-CS and CCG was successfully implanted around muscle of thigh without any significant immune response. Furthermore, no significant alterations were measured in serum parameters and the specific pathological features induced by most toxic compounds for liver and kidney toxicity. Therefore, these results suggest that SCT-CS showing good biocompatibility and non-toxicity can be successfully prepared from cellulose powder of SCT as well as has the potential for use as a powerful biomaterial for medical sutures.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.41 no.2
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• pp.1-6
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• 2009

The purpose of this study was to investigate effects of lignocellulosic fillers made of wood powder and inorganic fillers, such as GCC and PCC, on physical properties of papers. Mechanical treatment and chemical treatment were carried out subsequently for generating lignocellulosic fillers, and then inorganic filler and wood powder were mixed together, and then mechanically treated for making lignocellulosic fillers covered with inorganic fillers. Consequently the particle size of lignocellulosic fillers was higher than that of inorganic fillers, which led to lumen loading and simultaneously surface coverage of fine inorganic fillers. Lignocellulosic fillers contributed to the increase of both bulk and opacity of handsheets dramatically, but some of properties including tensile strength, brightness and roughness decreased compared to inorganic fillers.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.9
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• pp.923-928
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• 2015

In this paper, we propose an ultrasonic magnetic abrasive polishing (US-MAP) technique to effectively machine a high-strength material, and we prove the efficiency of hybrid finishing. We use Taguchi's experimental method to determine the influence of each parameter. Based on the results, US-MAP exhibited a higher polishing efficiency than traditional MAP, and a suitable frequency for hybrid finishing was 28 kHz. When investigating the effect of the parameters on the surface roughness, the ultrasonic amplitude had the greatest effect. However, when machining with $55-{\mu}m$ amplitude, the machining efficiency decreased as the magnetic flux density varied.

• Journal of the Korean Society for Railway
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• v.16 no.5
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• pp.379-385
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• 2013

In this study, partial drilled shafts (Bottom Cast-in-place Concrete pile) were applied to the pilot test site to ensure the bearing capacity; we used the skin friction force in the IGM to analyze the feasibility of the application of IGM theory. The soil characteristics were analyzed in cohesive, non-smear, and smooth conditions for the application of the IGM theory via geotechnical investigation and measurement of the disturbance and surface roughness. Static load and load transfer tests were conducted to calculate the allowable bearing capacity and the skin friction force by depth. The skin friction force increased with increase in the depth and standard settlement, showing a very high correlation. In addition, because the unconfined strength ($q_u$), which is the most important parameter in the cohesive IGM, cannot be measured in a weathered granite area, the static load and load transfer test results and the N value were used to obtain $q_u$.

• Tribology and Lubricants
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• v.16 no.2
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• pp.121-125
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• 2000

Silicon nitride ceramic has been verified as an excellent rolling bearing material because of its high strength and outstanding rolling fatigue life properties. However under some corrosive circumstances it showed drawbacks such as hardness reduction and severe wear caused by corrosion. In this work, the variations of the rolling wear and hardness of three kinds of ceramics were studied for the specimen aged 15 days in alkali water (90 $\pm$ 2$\^{C}$,25 wt% NaOH ). All of the specimens, ① Si$_3$N$_4$, ② 3Y-TZP and ③ 3Y-TZP alloyed with 5 wt% CeO$_2$, were sintered and post-HIPed, and then polished up to 0.02 $\mu$mRa of surface roughness. Rolling wear tests were conducted by MJ type rolling fatigue life tester under the initial theoretical maximum contact stress of 3.16 GPa and the spindle speed of 1,000 rpm. Spindle oil was used as a lubricant. The specimens were not worn before aging. For the specimen aged in alkali water, Si$_3$N$_4$ and 3Y-TZP were worn by rolling wear tests, and hardness was decreased. While aging the specimens, the phase was transformed from tetragonal to monoclinic in 3Y-TZP and the microstructure change occurred in Si$_2$N$_4$. 3Y-TZP specimens alloyed with 5 wt% CeO$_2$ were not worn after aging and no phase transformation occurred while aging.

• Applied Chemistry for Engineering
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• v.7 no.1
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• pp.194-202
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• 1996

Hot melt adhesive based on the polyamide resin was studied to improve the conventional hot melt adhesives such as ethylene-vinyl acetate which have inherent problems against creep and heat resistance. It was found that the terpolymer of nylons6, nylon66, and nylon12 or the nylon blend instead of nylon homopolymer was suitable base resin for hot melt adhesives, since the disruption of regularity in the polymer chains reduced the crystallinity, resulting in lower melting point and melt viscosity. Also, the rheological properties of the polyamide based hot melt adhesive could be controlled by the incorporation of terpene resin, butyl benzyl phthalate, and paraffin wax. The results of melt viscosities and tensile properties of adhesive itself indicated that the optimum adhesion properties could be obtained through the blending of CM831/843P resins with weight ratio 75/25~50/50. The adhesion between steel and steel was tested by using lap shear geometry. It was found that the surface roughness of steel affected the adhesion strength.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.5
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• pp.427-433
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• 2017

In the case of high-strength or low thermal conductivity material milling, tool breakage occurs easily because of the high friction temperature. Therefore, the effectiveness of the coolant supply is very important for proper tool cooling. As the manually adjustable joint mechanism nozzle is generally used for coolant supply, the cooling efficiency is very low. It also has a bad influence on the workspace environment because of coolant scattering. In this study, the milling characteristics of STS316L were investigated according to the coolant spray position based on the automatic adjustable system. Tool wear and surface roughness were measured according to the coolant spray position. Through these experiments, the effectiveness of the fabricated system was explained.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.31-39
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• 2008

To develop the MEMS cap bonding process without cavity formation, we electroplated Cu/Sn rim structures and measured the bonding characteristics for the Cu/Sn rims of $25{\sim}400{\mu}m$ width. As the effective device-mounting area ratio decreased and the failure strength ratio increased for wider Cu/Sn rim, these two properties were estimated to be optimized for the Cu/Sn rim with 150 ${\mu}m$ width. Complete bonding was accomplished at the whole interfaces of the Cu/Sn packages with the rim widths of 25 ${\mu}m$ and 50 ${\mu}m$. However, voids were observed locally at the interfaces with the rim widths larger than 100 ${\mu}m$. Such voids were formed by local non-contact between the upper and lower rims due to the surface roughness of the electroplated Sn.

• Journal of the Korean Geotechnical Society
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• v.20 no.6
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• pp.29-40
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• 2004

The bearing capacity of drilled shaft is affected by several factors, such as shaft length, shape, surface roughness, young's modulus of geomaterials and shaft, soil strength, confining stress and so on. However, there has been no design method of drilled shaft considering all factors mentioned above. Moreover, since geomaterials are simply classified as sand, clay and rock, there was no design criterion for IGM (Intermediate Geomaterials). Therefore, the rigorous design approach of drilled shaft was not possible by classical design method. However, since these characteristics were not considered in classical theories, bearing capacity was generally different ken practical value. In this study, the bearing capacity of drilled shaft with the IGM's theory was compared with those of classical theories. The results showed that classical method showed smaller values of bearing capacity than those of field load transfer data. Moreover, the evaluated value of bearing capacity with IGM theory corresponded fairly well with those of field data.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6C
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• pp.241-250
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• 2011

The design method of IGM proposed by FHWA to predict bearing capacities of drilled shaft socketed in weathered granite has been used generally. In this study, site investigations were performed in a pilot test site, and disturbance and roughness were measured. Geotechnical properties were assorted as cohesive material and undisturbed and smooth surface. A simple relationship was proposed to predict unconfined strength ($q_u$) of weathered granite using static load test results, load transfer test results and N values. It was confirmed that the design method to estimate bearing capacities of drilled shaft could improve IGM's theory for weathered granite from this research.