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Kang, Minji,Kim, Sungwhan,Kim, Heejin,Song, Youngjun,Jung, Dongwook,Kang, Sunah,Seo, Ji-Hun,Nam, Sohee,Lee, Yan American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.8
<P>Quorum sensing (QS) inhibitor-based therapy is an attractive strategy to inhibit bacterial biofilm formation without excessive induction of antibiotic resistance. Thus, we designed Ca<SUP>2+</SUP>-binding poly(lactide-<I>co</I>-glycolide) (PLGA) microparticles that can maintain a sufficient concentration of QS inhibitors around hydroxyapatite (HA) surfaces in order to prevent biofilm formation on HA-based dental or bone tissues or implants and, therefore, subsequent pathogenesis. Poly(butyl methacrylate-<I>co</I>-methacryloyloxyethyl phosphate) (PBMP) contains both Ca<SUP>2+</SUP>-binding phosphomonoester groups and PLGA-interacting butyl groups. The PBMP-coated PLGA (PLGA/PBMP) microparticles exhibited superior adhesion to HA surfaces without altering the sustained release properties of uncoated PLGA microparticles. PLGA/PBMP microparticle-encapsulating furanone C-30, a representative QS inhibitor, effectively inhibited the growth of <I>Streptococcus mutans</I> and its ability to form biofilms on HA surface for prolonged periods of up to 100 h, which was much longer than either furanone C-30 in its free form or when encapsulated in noncoated PLGA microparticles.</P> [FIG OMISSION]</BR>
Development of real-time automatic sorting system for color PET recycling process
Youngjun Jeon,Sangwoo Um,Jaemin Yoo,Minseok Seo,Eugene Jeong,Woojin Seo,Daewon Kang,Hancheul Song,Kyung-Soo Kim,Soohyun Kim 제어로봇시스템학회 2020 제어로봇시스템학회 국제학술대회 논문집 Vol.2020 No.10
Pollution from discarded plastic has become a serious environmental problem. The Great Pacific garbage patch consisting of abandoned plastics is killing marine life. In addition, micro-plastics decomposed by solar UV radiation and waves can accumulate in the human body. Recycling plastic is accordingly a critical element of waste management. As part of the solution to this problem, factory automation in recycling plants to handle more waste faster is essential. The amount of reproduced raw plastics is proportional to the inlet speed of the plastics waste stream into a recycling process line. Furthermore, the quality of recycled products with reproduced raw plastics depends on the sorting purity through the line. Thus, an automated system should be capable of real-time classification of the plastics category and rapid manipulation for removing selected plastics. We propose a real-time sorting system for mixed color plastics by applying a machine learning algorithm and a parallel manipulator with a vacuum suction pad. The learning data and picking test samples were collected from a municipal waste disposal site at RM corporation factory. This work shows the feasibility of real-time plastics recycling automation and a future development direction.
Size-controlled BiOCl–RGO composites having enhanced photodegradative properties
Kang, Suhee,Pawar, Rajendra C.,Pyo, Youngjun,Khare, Varsha,Lee, Caroline Sunyong Taylor Francis 2016 Journal of experimental nanoscience Vol.11 No.4
<P>Visible light-active bismuth oxychloride-reduced graphene oxide (BiOCl-RGO) composite photocatalysts were synthesised using a hydrothermal method at low temperature, and at a low cost. This approach reduced the recombination of electron-hole pairs and thereby provided more efficient photocatalysts. The size of BiOCl structure was controlled by polyvinylpyrrolidone (PVP) addition. Furthermore, formation of nanosized BiOCl sheets and BiOCl-RGO composites were confirmed by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. Fabricated BiOCl-RGO composite with PVP exhibited better photocatalytic activity than pure BiOCl grown with and without PVP towards degradation of Rhodamine B (RhB). It was found that the composite photocatalyst degrades RhB completely within 310 min as compared with several hours for pure BiOCl. The improved photocatalytic performance of BiOCl-RGO composite was attributed to its high specific surface area (22.074 m(2) g(-1) and existence of polar surfaces, compared with 9.831 m(2) g(-1) for pure BiOCl). The analyses indicated that RGO helped to reduce recombination losses and improve electron transport. It also showed that presence of polar surfaces improved photocatalytic activity of BiOCl. Hence, BiOCl-RGO composite is a promising catalyst for the degradation of organic pollutants under visible light and could be used in applications such as water purification devices.</P>
YoungJun Moon,Daekeun Jeong,Jeongil Kang 국제물리치료연구학회 2019 Journal of International Academy of Physical Ther Vol.10 No.3
Background: Stroke patients require arm movement exercising for various stimulations in standing position for various stimulations rather than in a sitting position because they require integrated skillful movements, such as stretching, holding, and controlling. Objective: This study was conducted to provide foundational clinical data about lower limb global synkinesis in stroke patients using arm movements in a standing position. Design: Randomized controlled trial. Methods: The subjects were divided into a control group (n = 10) and an experimental group (n = 10), and a pre-test was conducted to evaluate leg global synkinesis (GS) and balance. Intervention method is stretching an arm to hold a ball, repeating supination and pronation of the hand only while maintaining the arm extended as much as possible, repeating shoulder abduction and adduction while holding the pegboard. This was followed by a three-week intervention during which re-measurement was conducted in the same way as was done for the pre-test. Results: The control group showed a significant difference in GS and balance during plantar flexion (p<.05), and the experimental group showed a significant difference in GS and balance during all movements (p<.05, p<.01, respectively). There was a significant difference in GS and balance between the two groups during dorsiflexion (p<.05, p<.01, respectively). Conclusion: The findings demonstrate that human arm movements in a standing position can reduce GS in the affected limb, and balance can be improved by stimulating the surrounding tissues of the affected limb and changing them positively.
Design of a shape memory composite(SMC) using 4D printing technology
Kang, Minkyu,Pyo, Youngjun,Jang, Joon young,Park, Yunchan,Son, Yeon-Ho,Choi, MyungChan,Ha, Joo wan,Chang, Young-Wook,Lee, Caroline Sunyong Elsevier 2018 Sensors and actuators. A Physical Vol.283 No.-
<P><B>Abstract</B></P> <P>A fused deposition modeling (FDM) tool was used to fabricate a shape memory composite (SMC) that combined a shape memory alloy (SMA) with a shape memory polymer (SMP). The SMA caused a shape memory effect due to a phase change between martensite and austenite phases, in turn due to a temperature change. Also, the SMP had a shape memory effect caused by changes in the proportions of hard and soft segments near the glass transition temperature (T<SUB>g</SUB>). Usually, common SMAs and SMPs are not reversible, so these materials do not go back to their original shapes once they are deformed. In this study, we fabricated 4D printing actuator via reversible SMC actuations using 3D printing technology. Nylon 12 was used as the 3D printing material in filament form. Moreover, the volume fraction of SMA to SMP was varied to find the optimum ratio for good operation cycles. A volume fraction of SMA:SMP of 1:5 showed the largest length change, of 8 mm, and the most rapid response time, of 4 s in overall dimension of 140mm×10mm×1mm (length×width×thickness).Thus, the SMC showed promising results for the application of stents and valve controllers that could be manufactured by 3D printing technology.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An 4D printed SMC actuator was fabricated using SMA and SMP with a FDM 3D printer. </LI> <LI> A volume fraction of SMA:SMP of 1:5 showed the largest length change of 8 mm, and the most rapid response time of 4 s. </LI> <LI> The reversible actuator mechanism explains the SMC actuation via each shape memory effect. </LI> <LI> SMC showed potential application for stents and valve controllers via 3D printing technology to achieve customized designs. </LI> </UL> </P>
YoungJun Park,Hongjin Kim,Joo-Young Chun,JooYoung Lee,YoungGun Pu,Kang-Yoon Lee 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.4
This paper presents a wide frequency range LLC resonant controller IC for LED backlight units. In this paper a new phase-domain resonance deviation prevention circuit (RDPC), which covers a wide frequency and input voltage range, is proposed. In addition, a wide range gate clock generator and an automatic dead time generator are proposed. The chip is fabricated using 0.35 μm BCD technology. The die size is 2 x 2 mm2. The frequency of the clock generator ranges from 38 kHz to 400 kHz, and the dead time ranges from 300 ns to 2 μs. The current consumption of the LLC resonant controller IC is 4 mA for a 100 kHz operation frequency using a supply voltage of 15 V.