• Advances in nano research
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• 제13권3호
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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.

• 한국정보전자통신기술학회논문지
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• 제15권5호
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• pp.387-395
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• 2022

PDRN(Polydeoxyribonucleotide)은 조직재생 활성물질로 손상된 세포 및 조직의 자가 재생을 촉진하는 DNA 유래의 중합물질이다. PDRN은 DNA를 다양한 물리적 또는 화학적 방법으로 작은 크기로 절단한 DNA 조각으로 체내 투여시 조직세포 표면의 adenosine A2A receptor 수용체를 자극하여 세포 재생을 촉진하며 상처를 빠르게 회복시키고, 통증도 감소시키는 효과가 있다. 보통 어류의 정소나 정액으로부터 PDRN 추출을 하지만 본 연구에서는 다양한 식물에서 PDRN 추출 실험을 진행하였다. 실험 결과, 7종의 식물에서 PDRN 수율과 순수도는 단위 식물 중량 당 쑥갓이 가장 높았고, 브로콜리가 그 다음으로 우수했다. 이 두 식물의 PDRN을 대상으로 시험관에서 wound healing assay를 진행하여 PDRN의 효능을 분석한 결과, ㎍/ml 수준의 쑥갓과 브로콜리의 PDRN가 유의하게 wound healing 활성이 높음을 확인하였다. 본 연구의 결과는 이들 식물 유래 PDRN이 연어와 같은 어류 유래의 PDRN의 대체제로 사용할 수 있음을 의미한다.

• Composites Research
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• 제35권6호
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• pp.365-370
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• 2022

전기자동차 및 E-모빌리티 시장이 급속히 성장함에 따라 리튬이온전지는 현재 가장 주목받는 기술 중 하나로 여겨지고 있다. 따라서 높은 용량 및 출력, 급속 충전 성능을 가지는 고에너지밀도 전극 개발이 매우 중요한 상황이다. 고에너지밀도 전극 구현을 위해서 음극의 경우 실리콘, 주석 등 고용량 활물질 소재에 대한 연구가 진행되고 있는 상황이다. 하지만 이러한 고용량 활물질 소재는 전지의 충방전 과정 시 발생하는 부피팽창이 전지의 성능을 저하시키는 주된 원인이 된다고 알려져 있다. 따라서 활물질의 부피팽창을 완화할 수 있는 바인더 소재 개발이 매우 중요한 상황이며, 기존 PVDF, CMC/SBR계 바인더 뿐만 아니라 수용성 고분자(polyacrylic acid, polyvinyl alcohol, aliginate 등)를 이용한 바인더 소재 개발 연구가 많이 보고되고 있다. 이처럼 앞으로 리튬이온전지의 고성능화를 위해서 바인더는 매우 중요한 기술이 되었으며, 본 논문에서는 리튬이온전지용 음극 바인더 소재의 연구 동향을 살펴보고자 한다.

• 한국염색가공학회지
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• 제33권4호
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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.

• 한국항행학회논문지
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• 제27권1호
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• pp.71-76
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• 2023

본 논문에서는 마이크로스트립 패치 안테나와 폴리비닐알코올(PVA; polyvinyl alcohol)을 이용한 습도 센서에 대하여 연구하였다. PVA는 습도에 따라 유전율이 변하는 고분자 물질이며, 전계 변화에 민감한 마이크로스트립 패치 안테나의 방사면에 직사각형 슬롯을 추가하여 비유전율 변화에 대한 감도를 높였다. 0.76 mm 두께의 RF-35 기판에 제작된 안테나의 직사각형 슬롯이 추가된 방사면 주변을 PVA로 얇게 코팅한 후, 온습도 챔버를 사용하여 25도에서 상대습도를 40%에서 80%까지 10% 간격으로 증가시켜 안테나 입력 반사 계수의 공진 주파수와 크기의 변화를 측정하였다. 실험 결과, 상대습도가 40%에서 80%로 증가할 때 안테나 입력 반사 계수의 공진 주파수는 2.447 GHz에서 2.418 GHz로 감소하였고, 입력 반사 계수의 크기는 -7.112 dB에서 -3.428 dB로 증가하였다.

• Advances in materials Research
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• 제11권4호
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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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• 제27권1호
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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.

• 대한화장품학회:학술대회논문집
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• 대한화장품학회 2003년도 IFSCC Conference Proceeding Book I
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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.

• 한국결정성장학회지
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• 제33권4호
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• pp.139-144
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• 2023

무기충진제와 가소성 폴리머로 이루어진 스톤페이퍼는 기존 종이의 원료인 펄프를 사용하지 않아 자연보존에 기여하고 생분해성을 가지게 되면 보다 친환경적인 소재로 사용이 가능하다. 현재 대부분의 스톤페이퍼는 가열압출성형법으로 제조하고 있어 작업성을 증진시키기 위해 세라믹 충진제의 양이 제한되어 다양한 물성을 가질 수 없다. 본 연구에서는 이러한 스톤페이퍼 조성을 용제를 사용한 액상으로 제조하게 됨으로써 세라믹 충진제 첨가량에 제한이 적고 생분해성 조절을 위한 첨가제 투입도 용이하였다. 폐패각인 굴껍질을 열처리하여 무기충진제로 사용하였고, 재활용 소재로도 쉽게 구할 수 있는 폴리비닐클로라이드를 유기결합제로 사용하였다. 일반적인 폴리비닐클로라이드용 유기용제를 사용하여 폴리비닐클로라이드를 용해시킨 후 무기충진제와 생분해성을 부여하기 위한 셀룰로스를 혼합하여 시트 형태로 가공하여 용제기반 스톤페이퍼를 제조하여 그 물성에 대해 분석하였다.

• Journal of Korean Dental Science
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• 제16권1호
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• pp.23-34
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• 2023

Purpose: This study aims to investigate the force delivery profile of thermoformed aligners (TFA) compared with direct-printed aligners (DPA) and to explore the effect of different activation amounts on forces and moments of respective groups. A secondary objective is to observe the amount of stress relaxation that occurs over the 7~14 days when aligners are maintained in a simulated intraoral environment. Materials and Methods: An in vitro setup was created to quantify forces and moments. It consisted of a three dimensional-printed base plate and segmented maxillary teeth, placed in a semi-enclosed chamber to maintain a temperature of 37℃. Ninety clear aligners were divided into nine groups of ten aligners each based on material types (Zendura, ATMOS, TC-85) and activation amounts. Aligners were created with 0.00, 0.25- and 0.50-mm activations for lingual bodily movement of the upper left central incisor and kept on models in the "stressed" position in a 37℃ water bath. Three force components acting on the upper left lateral incisor, upper left central incisor, and upper right central incisor were measured for each time point, beginning from the initial baseline measurement, 8 hours, 16 hours, 24 hours, 2 days, 3 days, 4 days, 5 days, 6 days, 7 days, and lastly, 14 days. Result: TC-85 aligners in every activation group showed less force on teeth than Zendura and ATMOS. Significant force levels from 0.0 mm activation were present and stayed consistent over the course of 14 days. Comparisons made for baseline measurements to 7-days and 14-days showed statistically significant change from the baseline force level. Conclusion: TC-85 aligners demonstrated lower, more consistent forces with fewer side effects. Aligners can generate forces even when no activation is programmed. No major decreases in force levels over time were observed; the intra-oral clinical simulated environment and length of observation time could contribute to this.