• Steel and Composite Structures
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• v.38 no.5
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• pp.477-496
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• 2021

The main objective of this paper is to study vibration of sandwich open cylindrical panel with damaged core and FG face sheets based on three-dimensional theory of elasticity. The structures are made of a damaged isotropic core and two external face sheets. These skins are strengthened at the nanoscale level by randomly oriented Carbon nanotubes (CNTs) and are reinforced at the microscale stage by oriented straight fibers. These reinforcing phases are included in a polymer matrix and a three-phase approach based on the Eshelby-Mori-Tanaka scheme and on the Halpin-Tsai approach, which is developed to compute the overall mechanical properties of the composite material. Three complicated equations of motion for the panel under consideration are semi-analytically solved by using 2-D differential quadrature method. Several parametric analyses are carried out to investigate the mechanical behavior of these multi-layered structures depending on the damage features, through-the-thickness distribution and boundary conditions. It is seen that for the large amount of power-law index "P", increasing this parameter does not have significant effect on the non-dimensional natural frequency parameters of the FG sandwich curved panel. Results indicate that by increasing the value of isotropic damage parameter "D" up to the unity (fully damaged core) the frequency would tend to become zero. One can dictate the fiber variation profile through the radial direction of the sandwich panel via the amount of "P", "b" and "c" parameters. It should be noticed that with increase of volume fraction of fibers, the frequency parameter of the panels does not increase necessarily, so by considering suitable amounts of power-law index "P" and the parameters "b" and "c", one can get dynamic characteristics similar or better than the isotropic limit case for laminated FG curved panels.

• Advances in nano research
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• v.13 no.3
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• pp.285-295
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• 2022

Creation of plastic deformation under seismic loads, is one of the most serious subjects in RC structures with steel bars which reduces the life threatening risks and increases dissipation of energy. Shape memory alloy (SMA) is one of the best choice for the relocating plastic hinges. In a challenge to study the seismic response of concrete moment resisting frame (MRF), this article investigates numerically a new type of concrete frames with nano fiber reinforced polymer (NFRP) and shape memory alloy (SMA) hinges, simultaneously. The NFRP layer is containing carbon nanofibers with agglomeration based on Mori-Tanaka model. The tangential shear deformation (TASDT) is applied for modelling of the structure and the continuity boundary conditions are used for coupling of the motion equations. In SMA connections between beam and columns, since there is phase transformation, hence, the motion equations of the structure are coupled with kinetic equations of phase transformation. The Hernandez-Lagoudas theory is applied for demonstrating of pseudoelastic characteristics of SMA. The corresponding motion equations are solved by differential cubature (DC) and Newmark methods in order to obtain the peak ground acceleration (PGA) and residual drift ratio for MRF-2%. The main impact of this paper is to present the influences of the volume percent and agglomeration of nanofibers, thickness and length of the concrete frame, SMA material and NFRP layer on the PGA and drift ratio. The numerical results revealed that the with increasing the volume percent of nanofibers, the PGA is enhanced and the residual drift ratio is reduced. It is also worth to mention that PGA of concrete frame with NFRP layer containing 2% nanofibers is approximately equal to the concrete frame with steel bars.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.5
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• pp.387-395
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• 2022

PDRN (Polydeoxyribonucleotide) is a DNA-derived polymer that promotes self-renewal of damaged cells and tissues as a tissue regeneration active material. PDRN is a DNA fragment cut into small sizes by various physical or chemical methods. When administered to the body, PDRN binds and stimulates the adenosine A2A receptor on the surface of tissue cells to promote cell regeneration, accelerate wound healing, and reduce pain. Although PDRN is prepared from testis or semen of fish in most cass, PDRN extraction from various plants species was performed in the present study. Among 7 tested plant species, the highest DNA yield and purity was obtained form mugwort (Chrysanthemum coronarium, C.c), followed by broccoli (Brassica oleracea, B.o). Then, we evaluated the in vitro wound healing capacity of PDRNs prepared from these two selected plants. PDRN from C.c and B.o. significantly stimulated the wound healing process at ㎍/ml range. The present study suggests that PDRN from plant species can be an effective alternative to PDRN from marine organism.

• Composites Research
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• v.35 no.6
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• pp.365-370
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• 2022

According to the rapid growth of electric vehicle (EVs) and E-mobility market, Li-ion batteries are one of the most progressive technologies. The demand of LIBs with high energy capacity, rate performance and fast charging is continuously increasing, hence high-performance LIBs should be developed. Si is considered as the most promising anode material to improve energy density because of its high theoretical capacity. However, Si suffers large volume chances during the charging and discharge process, leading to the fast degradation of cycle performance. Therefore, polymeric binders play a key role in electrochemical performance of Si anode by efficiently enduring the Si expansion and maintaining the binding networks in electrode. In this review, we explain the role of polymeric binders in electrode and introduce the anode binders with enhanced mechanical and chemical properties which can improve electrochemical performances of Si-based anode.

• Textile Coloration and Finishing
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• v.33 no.4
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• pp.191-201
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• 2021

In this study, an eco-friendly indigo reduction system(scale up reduction, use of buffer solution, and pH control) using baker's yeast(Saccharomyces cerevisiae) was applied for natural indigo(Polygonum tinctorium) dyeing of Hanji fabric and Hanji-mixture fabric(Hanji/Cotton, Hanji/Silk). The effect of concentration of baker's yeast, repeat dyeing, and bath reuse was investigated in terms of dye uptake indicating reduction power. And the oxidation-reduction potential(ORP) was monitored. We also evaluated color properties and colorfastness according to the color strength. The yeast concentration did not significantly affect the maximum reduction power. However, the highest yeast concentration was effective in improving the initial dye uptake, and its the reduction retention power was the most excellent. Even on the last reduction day, the effect of increasing the dye uptake by repeat dyeing was observed. And it was confirmed that the reduction bath could be reused for up to 30 days by supplementing yeast at the end of reduction. For all the fabrics used, deeper and darker PB color were obtained by repeat dyeing. As dyeing was repeated, purplish tint got stronger on the Hanji/Silk fabric compared to other fabrics. Regardless of the composition of Hanji fabrics and color strength, washing and dry cleaning fastness were relatively good with above rating 4-5, and fastness to rubbing and light were acceptable with a rating 3-4 ~ 4-5. The eco-friendly natural indigo dyeing process using niram and baker's yeast would offer global marketability and diversity of Hanji product as a sustainable high value-added material.

• Journal of Advanced Navigation Technology
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• v.27 no.1
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• pp.71-76
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• 2023

In this paper, a humidity sensor using a microstrip patch antenna(MPA) and polyvinyl alcohol(PVA) is studied. PVA is a polymer material whose permittivity changes with humidity, and a rectangular slot is added to the radiating edge of the MPA, which is sensitive to changes in electric field, in order to increase the sensitivity to changes in relative permittivity. After thinly coating the area around the radiating edge with the rectangular slot of the MPA fabricated on a 0.76 mm-thick RF-35 substrate with PVA, the changes in the resonant frequency and magnitude of the MPA's input reflection coefficient are measured when relative humidity is adjusted from 40% to 80% in 10% increments at a temperature of 25 degrees using a temperature and humidity chamber. Experiment results show that when the relative humidity increases from 40% to 80%, the resonance frequency of the antenna' input reflection coefficient decreases from 2.447 GHz to 2.418 GHz, whereas the magnitude increases from -7.112 dB to -3.428 dB.

• Advances in materials Research
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• v.11 no.4
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• pp.375-390
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• 2022

Carbon Fiber Reinforced Polymer (CFRP) composite provides outstanding mechanical capabilities and is therefore popular in the automotive and aerospace industries. Drilling is a common final production technique for composite laminates however, drilling high-strength composite laminates is extremely complex and challenging. The delamination of composites during the drilling at the entry and exit of the hole has a severe impact on the results of the holes surface and the material properties. The major goal of this research is to investigate contemporary industry solutions for drilling CFRP composites: enhanced edge geometries of cutting tools. This study examined the occurrence of delamination at the entry and exit of the hole during the drilling. For each of the 80°, 90°, and 118°point angle uncoated Brad point, Dagger, and Twist solid carbide drills, Taguchi design of experiments were undertaken. Cutting parameters included three variable cutting speeds (100-125-150 m/min) and feed rates (0.1-0.2-0.3 mm/rev). Brad point drills induced less delamination than dagger and twist drills, according to the research, and the best cutting parameters were found to be a combination of maximum cutting speed, minimum feed rate, and low drill point angle (V:150 m/min, f: 0.1 mm/rev, θ: 80°). The feed rate was determined to be the most efficient factor in preventing hole entry and exit delamination using analysis of variance (ANOVA). Regression analysis was used to create first-degree mathematical models for each cutting tool's entrance and exit delamination components. The results of optimization, mathematical modelling, and experimental tests are thought to be reasonably coherent based on the information obtained.

• The Korean Journal of Physiology and Pharmacology
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• v.27 no.1
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• pp.31-38
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• 2023

Carboplatin, an advanced anticancer drug with excellent efficacy against ovarian cancer, was developed to alleviate the side effects that often occur with cisplatin and other platinum-based compounds. Our study reports the in vitro characteristics, viability, and activity of cells expressing the inducible nitric oxide synthase (iNOS) gene after carboplatin was conjugated with polysuccinimide (PSI) and administered in combination with other widely used anticancer drugs. PSI, which has promising properties as a drug delivery material, could provide a platform for prolonging carboplatin release, regulating its dosage, and improving its side effects. The iNOS gene has been shown to play an important role in both cancer cell survival and inhibition. Herein, we synthesized a PSI-carboplatin conjugate to create a modified anticancer agent and confirmed its successful conjugation. To ensure its solubility in water, we further modified the structure of the PSI-carboplatin conjugate with 2-aminoethanol groups. To validate its biological characteristics, the ovarian cancer cell line SKOV-3 and normal ovarian Chinese hamster ovary cells were treated with the PSI-carboplatin conjugate alone and in combination with paclitaxel and topotecan, both of which are used in conventional chemotherapy. Notably, PSI-carboplatin conjugation can be used to predict changes in the genes involved in cancer growth and inhibition. In conclusion, combination treatment with the newly synthesized polymer-carboplatin conjugate and paclitaxel displayed anticancer activity against ovarian cancer cells but was not toxic to normal ovarian cancer cells, resulting in the development of an effective candidate anticancer drug without severe side effects.

• Proceedings of the SCSK Conference
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• 2003.09a
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• pp.700-718
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• 2003

Fructan, a polysaccharide existing in plants or produced by microorganisms, is a sugar polymer of fructose with $\beta$-2,6 linkages. In this study, we investigated some cosmeceutical properties of Fructan such as moisturizing effect, cell proliferation effect, anti-inflammation effect and cell cytotoxicity. Zymomonas mobilis, a microorganism producing Fructan, was cultured in a medium containing 10％ sucrose and 2％ yeast extract as main components for 24 hours at 37$^{\circ}C$ and pH 7. Fructan was obtained by precipitation from the cultured medium by adding alcohol (alcohol ratio of 1:3) after removing the enzyme by centrifuging. Fructan exhibited almost same moisturizing effect as hyaluronic acid and cell proliferation effect on human fibroblast and keratinocyte as well. Moreover, on cell proliferation test on bio-artificial skin constructed by 3-dimensional(3-D) culture after inducing primary skin inflammation with 0.5％ sodium lauryl sulfate (SLS), the 3-D artificial skin treated with 0.01 mg/ml, 0.05mg/ml of Fructan exhibited higher cell proliferation than the 3-D artificial skin treated with SLS only. On anti-inflammation test on 3-D artificial skin evaluated by measuring secreted quantity of interleukin-1$\alpha$ (IL-1$\alpha$) which is a pre-inflammatory mediator induced by SLS, the quantity of IL-1$\alpha$on the 3-D artificial skin treated with 0.01 mg/ml, 0.05mg/ml of Fructan was less than the one on the 3-D artificial skin treated with SLS only. As a result of these studies, Fructan has anti-inflammation effect against inflammatory reaction by a skin irritant as well as cell proliferation effect in bio-artificial skin. Fructan was also evaluated as a safe material without any toxicity in safety tests using fibroblasts and animals.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.4
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• pp.139-144
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• 2023

Stone papers made of inorganic filler and plastic polymer do not use pulp, which is the main raw material of existing papers, so they contribute to the preservation of nature and can be used as more eco-friendly materials when they have biodegradability. Since most stone papers are manufactured by hot extrusion, the amount of ceramic fillers and related physical properties are limited to control manufacturing workability. In this study, the stone paper composition was prepared in a liquid form using solvents, so that there was little limitation on the amount of ceramic filler added and it was also easy to add additives to control biodegradability. They were fabricated from eco-friendly raw materials using waste oyster shells as an inorganic filler and (recyclable) PVC materials as an organic binder. After making a solution using common solvents for PVC, inorganic filler and cellulose to impart biodegradability were mixed and processed into sheets to prepare solvent-based stone papers, and their paper properties were evaluated.