• 전력전자학회논문지
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• 제20권6호
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• pp.573-579
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• 2015

A control algorithm of thyristor dual converter power system is proposed in this study for a railway power substation. The thyristor dual converter can use regenerative power without an additional system using control algorithm. An autonomous voltage and mode change method is also proposed to provide uninterrupted power to the railway. A 10 kW reduced model of the thyristor dual converter power system is built and tested to verify the validity of the proposed control algorithm.

• Journal of Microbiology and Biotechnology
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• 제34권5호
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• pp.1003-1016
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• 2024

This study explores the potential of plant-based decellularization in regenerative medicine, a pivotal development in tissue engineering focusing on scaffold development, modification, and vascularization. Plant decellularization involves removing cellular components from plant structures, offering an eco-friendly and cost-effective alternative to traditional scaffold materials. The use of plant-derived polymers is critical, presenting both benefits and challenges, notably in mechanical properties. Integration of plant vascular networks represents a significant bioengineering breakthrough, aligning with natural design principles. The paper provides an in-depth analysis of development protocols, scaffold fabrication considerations, and illustrative case studies showcasing plant-based decellularization applications. This technique is transformative, offering sustainable scaffold design solutions with readily available plant materials capable of forming perfusable structures. Ongoing research aims to refine protocols, assess long-term implications, and adapt the process for clinical use, indicating a path toward widespread adoption. Plant-based decellularization holds promise for regenerative medicine, bridging biological sciences with engineering through eco-friendly approaches. Future perspectives include protocol optimization, understanding long-term impacts, clinical scalability, addressing mechanical limitations, fostering collaboration, exploring new research areas, and enhancing education. Collectively, these efforts envision a regenerative future where nature and scientific innovation converge to create sustainable solutions, offering hope for generations to come.

• 전력전자학회논문지
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• 제22권1호
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• pp.9-17
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• 2017

A parallel control algorithm of thyristor dual-converter power system for the DC power supply of railway is proposed. The circulating current and current imbalance generated during parallel operation can be limited to control the output voltage of each power system by using the proposed parallel control algorithm. The proposed control algorithm can also eliminate output current sensor to achieve the same output response without additional costs. The validity of the proposed algorithm is verified through simulation and experiment.

• 한국표면공학회지
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• 제57권4호
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• pp.234-253
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• 2024

As the population ages, the importance of effective bone disease treatments is increasing, highlighting the role of bone grafts. Bone grafts are categorized into natural (autografts, allografts, xenografts) and synthetic (ceramics, polymers). Natural grafts have excellent regenerative abilities but pose biological risks, while synthetic grafts are biocompatible but less effective in regeneration. Various studies aim to enhance the safety and efficacy of bone grafts, significantly altering their surface properties. This review examines these studies and the resulting surface changes, aiming to guide future research and clinical applications.

• BMB Reports
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• 제55권7호
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• pp.336-341
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• 2022

Narrowing of arteries supplying blood to the limbs provokes critical hindlimb ischemia (CLI). Although CLI results in irreversible sequelae, such as amputation, few therapeutic options induce the formation of new functional blood vessels. Based on the proangiogenic potentials of stem cells, in this study, it was examined whether a combination of dental pulp stem cells (DPSCs) and human umbilical vein endothelial cells (HUVECs) could result in enhanced therapeutic effects of stem cells for CLI compared with those of DPSCs or HUVECs alone. The DPSCs+ HUVECs combination therapy resulted in significantly higher blood flow and lower ischemia damage than DPSCs or HUVECs alone. The improved therapeutic effects in the DPSCs+ HUVECs group were accompanied by a significantly higher number of microvessels in the ischemic tissue than in the other groups. In vitro proliferation and tube formation assay showed that VEGF in the conditioned media of DPSCs induced proliferation and vessel-like tube formation of HUVECs. Altogether, our results demonstrated that the combination of DPSCs and HUVECs had significantly better therapeutic effects on CLI via VEGF-mediated crosstalk. This combinational strategy could be used to develop novel clinical protocols for CLI proangiogenic regenerative treatments.

• Korean Chemical Engineering Research
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• 제54권3호
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• pp.285-292
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• 2016

삼차원 프린팅(3D printing) 기술은 공학, 제조업, 교육, 예술, 그리고 바이오의학 같은 다양한 분야에 활용되고 있는 혁신적 기술이다. 프린팅 기술, 재료/생화학물질을 포함한 최근 기술의 진보는 생체적합성 물질, 세포, 지지체 성분의 3D 프린팅으로 복잡한 3D 기능성 조직과 장기를 제작할 수 있는 가능성을 보여주고 있다. 3D 바이오프린팅 기술은 신약 개발, 독성 연구를 위한 조직 모델의 제작에도 활용되고 있다. 3D 바이오프린팅 기술은 공학, 생체재료과학, 세포생물학, 생화학, 물리, 의학 같은 분야의 통섭이 필요한 연구 분야이다.

• International Journal of Stem Cells
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• 제15권3호
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• pp.247-257
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• 2022

Background and Objectives: Although human-induced pluripotent stem cells (hiPSC) can be efficiently differentiated into cardiomyocytes (CMs), the heterogeneity of the hiPSC-CMs hampers their applications in research and regenerative medicine. Retinoic acid (RA)-mediated signaling pathway has been proved indispensable in cardiac development and differentiation of hiPSC toward atrial CMs. This study was aimed to test whether RA signaling pathway can be manipulated to direct the differentiation into sinoatrial node (SAN) CMs. Methods and Results: Using the well-characterized GiWi protocol that cardiomyocytes are generated from hiPSC via temporal modulation of Wnt signaling pathway by small molecules, RA signaling pathway was manipulated during the differentiation of hiPSC-CMs on day 5 post-differentiation, a crucial time point equivalent to the transition from cardiac mesoderm to cardiac progenitor cells in cardiac development. The resultant CMs were characterized at mRNA, protein and electrophysiology levels by a combination of qPCR, immunofluorescence, flow cytometry, and whole-cell patch clamp. The results showed that activation of the RA signaling pathway biased the differentiation of atrial CMs, whereas inhibition of the signaling pathway biased the differentiation of sinoatrial node-like cells (SANLCs). Conclusions: Our study not only provides a novel and simple strategy to enrich SANLCs but also improves our understanding of the importance of RA signaling in the differentiation of hiPSC-CMs.

• 한국수소및신에너지학회논문집
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• 제24권4호
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• pp.320-325
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• 2013

TUnitized reversible fuel cells (URFC) combine the functionality of a fuel cell and electrolyzer in one unitized device. For a URFC with proton exchange membrane, a titanium (Ti)-felt is applied to the gas diffusion layer (GDL) substrate at the oxygen electrode, and additionally titanium (Ti)-powders and TiN-powders are loaded in the GDL substrate as a micro porous layer (MPL). Double porous layer with TiN MPL was not acceptable for the URFC because both of fuel cell performance and electrolysis performance are degraded. The double porous layer with Ti-powder loading in the Ti-felt substrate influence rearly for the electrolysis performance. In contrast, the change of pore-size distribution brings a significant improvement of fuel cell performance under fully humidification conditions. This fact indicates that the hydrophobic meso-pores in the GDL play an important role for mass transport.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2023년도 춘계학술발표대회
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• pp.8-10
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• 2023

삼킴장애는 음식물이 입에서 식도로 가지않고 걸리거나 기도(Trachea)로 흡입되는 문제를 갖는 상태이다. 특히 노인이나 신경계 질환을 앓는 환자의 경우 기도로 흡입된 음식덩이가 폐렴을 일으키고 결국에는 사망으로 이어지기에 적절한 치료와 관리가 요구된다. 보통 영상으로 판단할 수 있는 삼킴단계는 구강준비단계(Oral Preparatory Phase), 구강단계(Oral Phase), 인두단계(Pharyngeal Phase), 식도단계(Esophageal Phase) 4가지로 분류하고 삼킴장애는 침습(Penetration)과 흡인(Aspiration)으로 크게 2가지로 분류한다. 본 논문에서는 이러한 6가지 클래스를 가지는 삼킴장애 환자 비디오 파일을 라벨링하기 위한 웹 애플리케이션을 제안한다. 이를 구현하기 위해서 대용량 멀티프레임 이미지를 수신해서 분리하여 저장하도록 개발하였다. 또한 음식덩이를 정교하게 분할할 수 있도록 GrabCut 알고리즘을 적용하여 라벨링할 수 있도록 하였다. 차후 라벨러와 전문의 간의 협업이 가능하도록 라벨링 데이터의 상태를 관리할 수 있도록 개발하고자 한다.