• Korean Journal of Materials Research
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• v.30 no.7
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• pp.369-375
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• 2020

FDM 3D printing structures have rough surfaces and require post-treatment to improve the properties. Fumigation is a representative technique for removing surface unevenness. Surface treatment by fumigation proceeds by dissolving the surface of the protruding structure using a vaporized solvent. In this study, 3D printed PVB outputs are surface-treated with ethyl-alcohol fumigation. As the fumigation time increases, the surface flattens as ethanol dissolves the mountains on the surface of PVB and the surface valleys are filled with dissolved PVB. Through the fumigation process, the mechanical strength tends to decrease, and deformation rate increases. Ethanol vapor permeates into PVB, widening the distance between chains and resulting in weak bonding strength between chains. In order to confirm the effect of fumigation only, an annealing process is performed at 80 ℃ for 1, 5, 10, 30, and 50 minutes and the results of the fumigation are compared.

• Korean journal of food and cookery science
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• v.19 no.4
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• pp.511-520
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• 2003

This study was carried out to determine the effects of various contents of kiwifruit contents on the quality characteristics of mixed polysaccharide gels made from $\kappa$-carrageenan and locust bean gum. The color value, gelling temperature, melting temperature, break down rate, syneresis, rupture properties, TPA properties and sensory properties of mixed polysaccharide gels with various contents of kiwifruit contents were measured. As the kiwifruit contents was increased, the lightness (L), yellowness (b) and greenness (-a) of the mixed polysaccharide gels increased. There were no differences in the color values of gels during storage. As the kiwifruit content was increased, the gelling and melting temperatures of the mixed polysaccharide gels also increased. The mixed polysaccharide gels with high kiwifruit contents were difficult to melt, and it seemed that the addition of kiwifruit to the mixed polysaccharide gels could improve the thennal stability of the gels. The syneresis of the gel increased with increasing storage time, whereas the addition of kiwifruit to the gel resulted in suppression of syneresis. With regard to the rupture properties, stress, energy and strain, they were all decreased with increasing kiwifruit contents. The TPA properties, adhesiveness, hardness and chewiness increased and cohesiveness decreased with increasing kiwifruit contents. The results showed that the gel became tough and adhesive, and could be easily broken under small deformation, with increasing kiwifruit contents. The sensory evaluation showed that the green color, aroma, sweetness and sourness increased with increasing kiwifruit contents. The texture, adhesiveness, springiness and cohesiveness decreased, and brittleness and hardness increased, with increasing kiwifruit contents. The overall acceptability of the gel with 30% kiwifruit content was the highest. Thus, mixed polysaccharide gels made from kiwifruits could be useful, as the addition of kiwifruit to a mixed polysaccharide gel results in a good aroma, taste and stability, despite a lowering of the textural properties.

• Journal of Ocean Engineering and Technology
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• v.30 no.4
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• pp.277-286
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• 2016

The first part of this study found the tendencies of the mechanical properties of two arctic structural steels (EH32 and FH32). In the second part, the crashworthiness of stiffened panels scaled down from the side frame structure of a Korean research icebreaker was determined. A procedure for designing the shapes and sizes of the stiffened panels, mass and shape of a drop striker, and a large temperature chamber, and then manufacturing these, is introduced in detail. From impact bending tests for the stiffened panels, the residual permanent deformations and deformation histories over time were captured using manual measurement and video image analyses. Numerical simulations of the impact bending tests were carried out for three different finite element models, which were mainly composed of shell elements, solid elements, and solid elements, with welding beads. It was proven from a comparison of the test results and numerical simulation results that the solid element model with the welding bead consideration approached the test results in terms of the residual deformations as long as the strain rate effect was taken into account.

• Archives of Craniofacial Surgery
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• v.12 no.1
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• pp.17-21
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• 2011

Purpose: It is difficult to objectively evaluate the outcomes of plastic surgical procedures. The combination of aesthetic and medical factors makes outcome quantification difficult. In this study, fracture reduction accuracy was objectively evaluated in patients with zygomatic complex fractures. Patients satisfaction with the accuracy was also examined. In addition, the patients' overall satisfaction and discomfort due to complications were analyzed. Methods: Eighty-five patients who had surgeries via bicoronal incision for zygomatic complex fracture from March 2006 to December 2009 were included in this study. Two plastic surgeons evaluated the accuracy of the fracture reduction with postoperative computed tomography. A survey questionnaire was administered to evaluate the patients' overall satisfaction and the impact of symptoms associated with the procedure on the patients' daily lives. Results: The overall patient satisfaction rate was $82.1{\pm}10.9%$ (range, 45~100%). The level of deformation was $6.7{\pm}10.9%$, the levels of discomfort in daily life due to pain, paresthesia, scar, and facial palsy were $8.5{\pm}13.2%$, $5.8{\pm}8.9%$, $4.4{\pm}9.9%$, and $1.9{\pm}9.2%$, respectively. According to the visual analogue scale, paresthesia was found to be the most frequent symptom (43.5%), and pain was the most troublesome symptom. Conclusion: The use of bicoronal incision for treating zygomatic complex fractures can cause various complications due to wide incision and dissection. However, this technique can provide optimized reduction and rigid fixation. Most of these postoperative complications can cause significant discomfort in the patient. It is thought that the use of correct surgical technique and the accurate knowledge of craniofacial anatomy will result in a reduction of complications and significantly increase patient satisfaction.

• Korean Journal of Metals and Materials
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• v.50 no.11
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• pp.801-808
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• 2012

TiAlCN coatings with various C contents were synthesized by unbalanced magnetron sputtering. The characteristics, the crystalline structure, surface morphology, hardness, and friction coefficient of the coatings as a function of the C content were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), a microhardness tester, and a wear test. In addition, their corrosion behaviors in a deaerated 3.5 wt% NaCl solution at $40^{\circ}C$ were investigated by potentiodynamic polarization tests. The results indicated that the $Ti_{14.9}Al_{15.5}C_{30.7}N_{38.9}$ coating had the highest hardness, elastic modulus, and a plastic deformation resistance of 39 GPa, 359 GPa, and 0.55, respectively, and it also had the lowest friction coefficient of approximately 0.26. Comparative evaluation of the TiAlCN coatings indicated that a wide range of coating properties, especially coating hardness, could be obtained by the synthesis methods and processing variables. The microhardness of the coatings was much higher than that from previously reported coating using similar magnetron sputtering processes. It was almost as high as the microhardness measured from the TiAlCN coatings (~41 GPa) synthesized using an arc ion plating process. The potentiodynamic test showed that the corrosion resistance of the TiAlCN coatings was significantly better than the TiAlN coatings, and their corrosion current density ($i_{corr}$), corrosion potentials ($E_{corr}$) and corrosion rate decreased with an increasing C content in the coatings. The much denser microstructure of the coatings due to the increased amount of amorphous phase with increasing C contents in the coatings could result in the the improved corrosion resistance of the coatings.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.5
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• pp.297-304
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• 2019

In this research, crack propagation in a silicon anode during two-phase lithiation was evaluated using a cohesive zone model. The phase transition from crystalline silicon to lithiated silicon causes compressive yielding due to the high volume expansion rate. Li-ion diffuses from the surface of the silicon to its core, and the complex deformation mechanisms during lithiation cause tensile hoop stress along the surface. The Park-Paulino-Roesler (PPR) potential-based cohesive zone model that guarantees consistent energy dissipation in mixed-mode fracture was adopted to simulate edge crack propagation. It was confirmed that the edge crack propagation characteristics during lithiation from the FEM simulation results coincided with the real experimental results. Crack turning observed from real experiments could also be predicted by evaluating the angles of maximum tensile stress directions.

• Advances in Computational Design
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• v.4 no.4
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• pp.327-342
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• 2019

Rehabilitation and retrofitting of structures designed in accordance to standard design codes is an essential practice in structural engineering and design. For steel structures, one of the challenges is to strengthen the panel zone as well as its analysis in moment-resisting frames. In this research, investigations were undertaken to analyze the influence of the panel zone in the response of structural frames through a computational approach using ETABS software. Moment-resisting frames of six stories were studied in supposition of real panel zone, different values of rigid zone factor, different thickness of double plates, and both double plates and rigid zone factor together. The frames were analyzed, designed and validated in accordance to Iranian steel building code. The results of drift values for six stories building models were plotted. After verifying and comparing the results, the findings showed that the rigidity lead to reduction in drifts of frames and also as a result, lower rigidity will be used for high rise building and higher rigidity will be used for low rise building. In frames with story drifts more than the permitted rate, where the frames are considered as the weaker panel zone area, the story drifts can be limited by strengthening the panel zone with double plates. It should be noted that higher thickness of double plates and higher rigidity of panel zone will result in enhancement of the non-linear deformation rates in beam elements. The resulting deformations of the panel zone due to this modification can have significant influence on the elastic and inelastic behavior of the frames.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.4
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• pp.177-183
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• 2015

Incremental sheet metal forming is a manufacturing process to produce thin parts using sheet metals by a series of small incremental deformation. The process rarely needs dedicated dies and molds, thus, preparation time for the process is relatively short as to be compared to conventional metal forming. Spring back in sheet metal working is very common, which causes critical errors in dimensions. Incremental sheet metal forming is not fully investigated yet. Hence, incremental sheet metal forming frequently produces inaccurate parts. This paper proposes a method to minimize dimensional errors to improve shape accuracy of products manufactured by incremental forming. This study conducts experiments using an exclusive incremental forming machine and the material for these experiments are sheets of aluminum AL1015. This research defines a process parameter and selects a few factors for the experiments. The parameters employed in this paper are tool feed rate, tool diameter, step depth, material thickness, forming method, dies applied, and tool path method. In addition, their levels for each factor are determined. The plan of the experiments is designed using orthogonal array $L_8$ ($2^7$) which requires minimum number of experiments. Based on the measurements, dimensional errors are collected both on the tool contacted surfaces and on the non-contacted surfaces. The distances between the formed surfaces and the CAD models are scanned and recorded using a commercial software product. These collected data are statistically analyzed and ANOVAs (analysis of variances) are drawn up. From the ANOVAs, this paper concludes that the process parameters of tool diameter, forming depth, and forming method are the significant factors to reduce the errors on the tool contacted surface. On the other hand, the experimental factors of forming method and dies applied are the significant factors on the non-contacted surface. However, the negative forming method always produces better accuracy than the positive forming method.

• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.129-139
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• 2018

The Discrete Element Method (DEM) has been widely used in granular material researches. Especially, if material has a large deformation, such as ground, it can be a useful method to analyze. In this study, to simulate ground formations, DEM was used. The main purpose of DEM analysis was to investigate the numerical model which can predict the TBM performance by simulating excavating procedure. The selected EPB TBM has a 7.73 m of diameter and six spokes. And two pre-defined excavation conditions with the different rotation speeds per minute (RPM) of the cutterhead was applied. In the modeled cutterhead, the open ratio of cutterhead was 21.31% and number of cutters (including disc cutter and cutter bit) was 219. From the results, reaction forces and resistant torques at the cutterhead face and cutting tools, were measured and compared. Additionally the muck discharge rate and accumulated muck discharge by the screw auger were evaluated.

• Tribology and Lubricants
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• v.34 no.6
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• pp.279-283
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• 2018

In this study, we investigate the behavior of abrasive particles and change of the stick-slip pattern according to chemical mechanical polishing (CMP) process parameters when a large number of abrasive particles are fixed on a pad. The CMP process is simulated using the finite element method. In the simulation, the abrasive grains are composed of those used in the actual CMP process. Considering the cohesion of the abrasive grains with the start of the CMP process, abrasive particles with various sizes are fixed onto the pad at different intervals so that stick-slip could occur. In this analysis, we determine that when the abrasive particle size is relatively large, the stick-slip period does not change as the pressure increases while the moving speed is constant. However, if the size of the abrasive grains is relatively small, the amount of deformation of the grains increases due to the elasticity of the pad. Therefore, the stick-slip pattern may not be observed. As the number of abrasive particles increases, the stick-slip period and displacement decrease. This is consistent with the decrease in the von Mises yield stress value on the surface of the wafer as the number of abrasive grains increases. We determine that when the number of the abrasive grains increases, the polishing rate, and characteristics are improved, and scratches are reduced. Moreover, we establish that the period of stick-slip increases and the change of the stick-slip size was not large when the abrasive particle size was relatively small.