• Advances in nano research
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• v.7 no.5
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• pp.293-310
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• 2019

In this paper, thermal-buckling behavior of the functionally graded (FG) nanocomposite plates reinforced with graphene oxide powder (GOP) is studied under three types of thermal loading once the plate is supposed to be rested on a two-parameter elastic foundation. The effective material properties of the nanocomposite plate are considered to be graded continuously through the thickness according to the Halpin-Tsai micromechanical scheme. Four types of GOPs' distribution namely uniform (U), X, V and O, are considered in a comparative way in order to find out the most efficient model of GOPs' distribution for the purpose of improving the stability limit of the structure. The governing equations of the plate have been derived based on a refined higher-order shear deformation plate theory incorporated with Hamilton's principle and solved analytically via Navier's solution for a simply supported GOP reinforced (GOPR) nanocomposite plate. Some new results are obtained by applying different thermal loadings to the plate according to the GOPs' negative coefficient of thermal expansion and considering both Winkler-type and Pasternak-type foundation models. Besides, detailed parametric studies have been carried out to reveal the influences of the different types of thermal loading, weight fraction of GOP, aspect and length-to-thickness ratios, distribution type, elastic foundation constants and so on, on the critical buckling load of nanocomposite plates. Moreover, the effects of thermal loadings with various types of temperature rise are investigated comparatively according to the graphical results. It is explicitly shown that the buckling behavior of an FG nanocomposite plate is significantly influenced by these effects.

• Journal of the Korean Society of Safety
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• v.30 no.1
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• pp.34-39
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• 2015

The feasibility of recycling wasted printed circuit board (PCB) is investigated by preparing PCB added flame retardant composites filled with either unsaturated polyester or polyurethane. In order to improve electroconductive properties, copper powder was added into the composites, which results also in improving their antistatic properties. The prepared composite samples showed a binding between the polymer fillers observed by a scanning microscope. The sample group using unsaturated polyester is elastomeric that led to appreciable elongation and elasticity. In case of polyurethane, the tensile strength increased proportionally as increase of the amount of PCB powder. The composite materials can be utilized as antistatic composite materials, since the surface resistivity result showed increase of the electroconductive properties by adding Cu. The flammability of the samples is not satisfactory according to UL-94 vertical test. However, the flame retardant properties were improved by adding PCB power. This study, therefore, showed that it is feasible to fabricate polymer composite materials and improve the material characteristics by adding PCB powder, which can replace existing additives used for the preparation of polymer composite materials and can reduce the environment contamination by recycling the wasted PCB.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.9
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• pp.773-779
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• 2015

The laser Powder Bed Fusion (PBF) system is currently recognized as a leading process. Due to the various materials employed such as thermoplastic, metal and ceramic composite powder, the application's use extends to machinery, automobiles, and medical devices. The PBF system's surface quality of prototypes and processing time are significantly affected by several parameters such as laser power, laser beam size, heat temperature and laminate thickness. In order to develop a more elaborate and rapid system, this study developed a new PBF system and sintering process. It contains a 3-axis dynamic focusing scanner system that maintains a uniform laser beam size throughout the system unlike the $f{\theta}$ lens. In this study, experiments were performed to evaluate the effects of various laser scanning parameters and fabricating parameters on the fusion process, in addition to fabricating various 3D objects using a PA-12 starting material.

• The Korean Journal of Food And Nutrition
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• v.29 no.6
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• pp.1008-1014
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• 2016

This study was conducted with the purpose of investigating the rheological characteristics of noodle flour dough supplementary konjac powder comprising 0%, 0.5%, 1.0%, 1.5% or 2.0% of the total mixture. In farinograph analysis, water absorption increased with the increased content of konjac powder. Both the arrival times and the development times of the dough with added konjac powder were longer than original wheat flour dough. Dough stability was found to be increased as compared to the control, but decreased as konjac powder content was increased. As konjac powder content increased, the resistance of the dough as shown by farinograph data was highest in the original wheat flour dough as 130 BU. Starting temperature, maximum viscosity temperature and maximum viscosity were decreased as shown in amylograph analysis. In extensograph analysis, the dough's extensibility and resistance to extension of the dough decreased as the amount of konjac powder was increased. The ratio of resistance to extensibility (R/E) decreased with the an increase in the amount of konjac powder included in the dough. The dough's tensile strength after cooking was increased in proportion to the additional amount of konjac powder used.

• Journal of Powder Materials
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• v.22 no.4
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• pp.247-253
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• 2015

The sintering mechanisms of nanoscale copper powders have been investigated. A molecular dynamics (MD) simulation with the embedded-atom method (EAM) was employed for these simulations. The dimensional changes for initial-stage sintering such as characteristic lengths, neck growth, and neck angle were calculated to understand the densification behavior of copper nano-powders. Factors affecting sintering such as the temperature, powder size, and crystalline misalignment between adjacent powders have also been studied. These results could provide information of setting the processing cycles and material designs applicable to nano-powders. In addition, it is expected that MD simulation will be a foundation for the multi-scale modeling in sintering process.

• The Korean Journal of Food And Nutrition
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• v.30 no.2
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• pp.282-289
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• 2017

This study was conducted to investigate the noodle-making characteristics of a noodle dough with konjac powder added. The water-binding capacity was significantly increased by increasing amounts of the konjac powder. When the weight and volume of the noodles were measured after cooking, there was no difference between the control and konjac powder groups. Turbidity was significantly reduced in a concentration-dependent manner. Chromaticity, in the case of raw noodle lightness (L), decreased significantly, while redness (a) and yellowness (b) significantly increased. Cooked noodles also showed the same pattern of results, however, as a whole, the results were lower when compared to wet noodles. The texture characteristics of hardness and chewiness significantly increased by increasing concentrations of the konjac powder. Cohesiveness was determined to not be significantly different by observing the surface of the noodle with a scanning electron microscope. In a sensory evaluation of the cooked noodle, no significant differences in gloss, taste, hardness, springiness or overall acceptability were observed between the control and konjac powder groups. This study indicates the that addition of 1.5% konjac powder to noodle dough may improve the functionality and preference of noodles.

• Archives of Plastic Surgery
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• v.49 no.2
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• pp.258-265
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• 2022

Background Chitosan (CS) is a well-known antimicrobial dressing material. Moreover, widely used amniotic membranes contain growth factors beneficial for wound healing. Herein, we created a novel amnion-conjugated CS-alginate membrane dressing and tested its wound healing potency in a diabetic swine model. Methods The bovine amniotic powder growth factor contents were evaluated by protein assay, and the powder's wound healing effects were assessed in vitro by HaCaT cell scratch closure. In vivo, two minipigs developed streptozotocin-induced diabetes. Serial serum glucose measurements and intravenous glucose tolerance tests were performed to confirm their diabetic status. Twelve square-shaped wounds created on each pig's back were randomly divided into control (n = 4), CS (n = 4), and amnion-CS (AC; n = 4) groups and treated accordingly with different dressings. Wound healing in each group was assessed by measuring wound contraction over time, capturing wound perfusion with indocyanine green (ICG) angiography, and histologically analyzing inflammatory markers. Results Amniotic powder elution promoted HaCaT cell migration in the scratch wound model, suggesting its beneficial in vitro wound healing effects. In vivo, the CS and AC groups showed earlier wound contraction initiation and reepithelialization and earlier wound perfusion improvement by ICG angiography than the control group. Additionally, the wound size of the AC group at week 3 was significantly smaller than those in the control group. There was no significant difference in the numbers of acute and chronic inflammatory cells between the groups. Conclusion The amnion-conjugated CS-alginate membrane, as well as CS dressing alone, could be a favorable dressing option for diabetic wounds.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.9
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• pp.787-792
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• 2015

Recently, 3D printing technology is a hot issue in various industrial fields. According to the user's application, it allows for the free form fabrication method to be utilized in a wide range. The powder based fusion technique is one of the 3D printing methods. When using this method it is possible to apply the various binder jetting techniques such as piezo, thermal bubble jet, dispenser and so on. In this paper, a multi thermal bubble ink jet was integrated for jetting of powder binding material and developing a power fused 3D printing system. For high quality 3D printing parts, it needs an analysis and evaluation of the behavior of the thermal bubble ink jet head. In the experiment, a correlation between jetting binder quantity and layer thickness of powder was investigated, and a 3D part model was fabricated, which was used by measuring the scale factor.

• The Korean Journal of Food And Nutrition
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• v.34 no.4
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• pp.321-330
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• 2021

The purpose of this study was to investigate the quality characteristics of bread made with 1%, 3%, 5%, and 7% of Bigeumdo Seomcho powder (Spinacia oleracea L.). The pH of dough and bread decreased as the amount of addition increased; 7% indicated the lowest. The moisture level correlated negatively with the powder addition, but the difference was not statistically meaningful (p<0.05). As the amount of addition was increased, the intensity of color increased but the volume decreased. The brightness and redness of the bread decreased as the amount of addition increased. The volume, specific volume, and baking loss rate correlated negatively with the powder addition. Regarding springiness, cohesiveness, and gumminess, the experiment group was higher than the control group and they lowered as the addition amount increased. The brittleness showed positive correlation with the addition amount. Out of the amino acids of bread, glutamic acid showed the highest value as the amount of addition was increased. Overall, it is possible to produce bakery bread using functional ingredients.

• Food Science of Animal Resources
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• v.37 no.5
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• pp.726-734
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• 2017

This study investigated the meat quality and storage characteristics of pork loin marinated in grape pomace powder during different storage periods. The experimental design included six treatments : pork loin containing only 100% water (Control, C); pork loin containing a combination of 20% grape pomace and 80% water (T1); pork loin containing a combination of 40% grape pomace and 60% water (T2); pork loin containing a combination of 0.5% grape pomace powder and 95.5% water (T3); pork loin containing a combination of 1.0% grape pomace powder and 99.0% water (T4); and pork loin containing a combination of 2.0% grape pomace powder and 98.0% water (T5). The pork loins aged by grape pomace and grape pomace powder showed decreased crude protein, crude fat, crude ash, pH, redness, and yellowness values; however, their moisture, lightness, and shear force increased significantly. During cold storage, marination with grape pomace and grape pomace powder reduced the 2-thiobarbituric acid value, volatile basic nitrogen value, and total microbial count in pork loin. Thus, marination with grape pomace and grape pomace powder improved the meat quality and storage characteristics, and could be used to improve storage stability of pork loin.