http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Lee, Younghun,Lee, Sungho,Zhao, Xing Guan,Lee, Dongoh,Kim, Taemin,Jung, Hoeryong,Kim, Namsu Techno-Press 2018 Smart Structures and Systems, An International Jou Vol.22 No.2
In the last decade, there has been an exponential increase of scientific interest in smart additive manufacturing (AM) technology. Among the different AM techniques, one of the most commonly applied processes is digital light processing (DLP). DLP uses a digital projector screen to flash an ultraviolet light which cures photopolymer resins. The resin is cured to form a solid to produce parts with precise high dimensional accuracy. During the curing process, there are several process parameters that need to be optimized. Among these, the exposure time affects the quality of the 3D printed specimen such as mechanical strength and dimensional accuracy. This study examines optimal exposure times and their impact on printed part. It was found that there is optimal exposure time for printed part to have appropriate mechanical strength and accurate dimensions. The gel fraction and TGA test results confirmed that the improvement of mechanical properties with the increasing UV exposure time was due to the increase of crosslinked network formation with UV exposure time in acrylic resins. In addition, gel fraction and thermogravimetric analysis were employed to microscopically investigate how this process parameter impacts mechanical performance.
Younghun Lee,Sungho Lee,Xing Guan Zhao,Dongoh Lee,Taemin Kim,정회룡,Namsu Kim 국제구조공학회 2018 Smart Structures and Systems, An International Jou Vol.22 No.2
In the last decade, there has been an exponential increase of scientific interest in smart additive manufacturing (AM) technology. Among the different AM techniques, one of the most commonly applied processes is digital light processing (DLP). DLP uses a digital projector screen to flash an ultraviolet light which cures photopolymer resins. The resin is cured to form a solid to produce parts with precise high dimensional accuracy. During the curing process, there are several process parameters that need to be optimized. Among these, the exposure time affects the quality of the 3D printed specimen such as mechanical strength and dimensional accuracy. This study examines optimal exposure times and their impact on printed part. It was found that there is optimal exposure time for printed part to have appropriate mechanical strength and accurate dimensions. The gel fraction and TGA test results confirmed that the improvement of mechanical properties with the increasing UV exposure time was due to the increase of crosslinked network formation with UV exposure time in acrylic resins. In addition, gel fraction and thermogravimetric analysis were employed to microscopically investigate how this process parameter impacts mechanical performance.
Lee, Jung Woo,Viswan, Ravindranath,Choi, Yoon Jeong,Lee, Yeob,Kim, Se Yun,Cho, Jaehun,Jo, Younghun,Kang, Jeung Ku WILEY-VCH Verlag 2009 Advanced Functional Materials Vol.19 No.14
<P>Using conventional methods to synthesize magnetic nanoparticles (NPs) with uniform size is a challenging task. Moreover, the degradation of magnetic NPs is an obstacle to practical applications. The fabrication of silica-shielded magnetite NPs on carbon nitride nanotubes (CNNTs) provides a possible route to overcome these problems. While the nitrogen atoms of CNNTs provide selective nucleation sites for NPs of a particular size, the silica layer protects the NPs from oxidation. The morphology and crystal structure of NP–CNNT hybrid material is investigated by transmission electron microscopy (TEM) and X-ray diffraction. In addition, the atomic nature of the N atoms in the NP–CNNT system is studied by near-edge X-ray absorption fine structure spectroscopy (nitrogen K-edge) and calculations of the partial density of states based on first principles. The structure of the silica-shielded NP–CNNT system is analyzed by TEM and energy dispersive X-ray spectroscopy mapping, and their magnetism is measured by vibrating sample and superconducting quantum interference device magnetometers. The silica shielding helps maintain the superparamagnetism of the NPs; without the silica layer, the magnetic properties of NP–CNNT materials significantly degrade over time.</P> <B>Graphic Abstract</B> <P>Magnetite nanoparticles (NPs) of uniform size are anchored onto the outer surface of carbon nitride nanotubes (CNNTs) because the CNNT nitrogen atoms provide selective nucleation sites. Shielding the NP–CNNT hybrid materials with silica (see image on left) helps maintain the magnetic properties of the NPs; without a silica layer, the magnetic performance in water of the NP–CNNT materials significantly degrade over time (see plot on right). <img src='wiley_img/1616301X-2009-19-14-ADFM200801498-content.gif' alt='wiley_img/1616301X-2009-19-14-ADFM200801498-content'> </P>
Younghun Ko,Hong-Soo Cho,Sang-Sung Lee,So-Bong Shin,Yongchul Song,Sang-Gug Lee Institute of Electrical and Electronics Engineers 2016 IEEE transactions on power electronics Vol. No.
<P>In this paper, a flicker-free transformer-less multi-channel light-emitting diode (LED) driver that adopts a new power factor enhancement technique is presented. The proposed LED driver divides the transmission path of the current to the LED string in two ways depending on the instantaneous input voltage in order to improve the PF relative to that of a conventional compact flicker-free LED driver that uses a fixed LED current regulation scheme with only one electrolytic capacitor. The proposed driver can be implemented with a minimum number of external components leading to a compact module that allows a light bulb with omnidirectional light emission. In order to enhance the expandability of the smart bulb, a conventional buck converter with 3-V output is integrated with the proposed LED driver to supply the peripherals of the module. The proposed LED driver IC is implemented in a 0.35-mu m ultrahigh voltage CMOS process and occupies an area of 2.9 mm x 2.0 mm. A 10-W smart bulb prototype that adopts the proposed LED driver is flicker free and shows a power factor of 0.715 and power conversion efficiency of 77.5% for an ac supply of 120 V.</P>
Fabrication and ink-jet patterning of copper nanoparticles with improved dispersion stability.
Lee, Kun-Jae,Kim, Namwoo,Hong, Sung-Jei,Lee, Kyu Bok,Lee, Dong-Jun,Oh, Je Hoon,Byun, Younghun,Choa, Yong-Ho American Scientific Publishers 2010 Journal of nanoscience and nanotechnology Vol.10 No.5
<P>Copper (Cu) nanoparticles as the metal nanoparticles in the conductive ink were synthesized using electrochemical reaction. This method is characterized as the synthesis process without any metal salts and the post-treatment of washing and drying. It means that it does not need to consider about oxidized and agglomerated metal nanoparticles during the extra treatments. The Cu nanoparticles were synthesized in the various conditions of electrolyte to investigate the mechanism of the synthesis reaction of Cu nanoparticles. And also, the synthesized Cu nanoparticles were controlled the dispersion stability with the addition of dispersion agent such as PVP and Dextran. Finally, it was achieved the ink-jet printed Cu patterns using the synthesized Cu nanoparticles, and examined the morphology of the patterns.</P>
Lee Han-Jun,Hong Seok-Jin,Kim Seung-Soo,Kwon Young-Yon,Choi Bong-Hwan,Choi Kyung-Mi,Choi Kyung-Mi,Lee Myung-Jin,Hwang Sun-Young,Park Kyoungwan,Joo Younghun,Song Hwayoung,Lee Cheol-Koo 대한남성과학회 2022 The World Journal of Men's Health Vol.40 No.2
Purpose:Purpose: To build an age prediction model, we measured CD4+ and CD8+ cells, and humoral components in canine periph-eral blood. Materials and Methods:Materials and Methods: Large Belgian Malinois (BGM) and German Shepherd Dog (GSD) breeds (n=27), aged from 1 to 12 years, were used for this study. Peripheral bloods were obtained by venepuncture, then plasma and peripheral blood mono-nuclear cells (PBMCs) were separated immediately. Six myokines, including interleukin (IL)-6, IL-8, IL-15, leukemia inhibitory factor (LIF), growth differentiation factor 8 (GDF8), and GDF11 were measured from plasma and CD4+/CD8+ T-lymphocytes ratio were measured from PBMC. These parameters were then tested with age prediction models to find the best fit model. Results:Results: we found that the T-lymphocyte ratio (CD4+/CD8+) was significantly correlated with age (r=0.46, p=0.016). Among the six myokines, only GDF8 showed a significant correlation with age (r=0.52, p=0.005). Interestingly, these two markers showed better correlations in male dogs than females, and BGM breed than GSD. Using these two age biomarkers, we could obtain the best fit in a quadratic linear mixed model (r=0.77, p=3×10-6). Conclusions:Conclusions: Age prediction is a challenging task because of complication with biological age. Our quadratic linear mixed model using CD4+/CD8+ ratio and GDF8 level showed a meaningful age prediction.