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Carbon nanofiber-reinforced polymeric nanocomposites
Changwoon Jang,John Hutchins,Jaesang Yu 한국탄소학회 2013 Carbon Letters Vol.14 No.4
Five vapor-grown carbon nanofiber (VGCNF) reinforced vinyl ester (VE) nanocomposite configurations were fabricated, imaged, and mechanically tested in order to obtain information on the influence and the interactions of the role of the microstructure at lower length scales on the observed continuum level properties/response. Three independent variables (the nanofiber weight fraction and two types of nanofiber mixing techniques) were chosen to be varied from low, middle, and high values at equally spaced intervals. Multiple mixing techniques were studied to gain insight into the effect of mixing on the VGCNF dispersion within the VE matrix. The point count method was used for both lower length-scale imaging techniques to provide quantitative approximations of the magnitude and the distribution of such lower length-scale features. Finally, an inverse relationship was shown to exist between the stiffness and strength properties of the resulting nanocomposites under uniaxial quasistatic compression loading.
장필호(Pilho Jang),김용환(Yongwan Kim),전성규(Sungkyu Jun),이창운(Changwoon Lee),정명진(Myungjin Jung) 한국IT서비스학회 2020 한국IT서비스학회지 Vol.19 No.2
The development of digital technology is changing the paradigm of the healthcare industry to preventive and consumer-oriented. The combination of the ICT industry and the bio-healthcare industry is emerging as a core industry in the era of the Fourth Industrial Revolution. The Korean government has also selected the bio-healthcare industry as one of the three key future development industries. In May, the government announced its bio-health industry innovation strategy and set a goal of 300,000 employees. Therefore, analyzing the effects of employment on the related industries of the digital bio-healthcare industry is very important for the establishment of future industrial and technology development policies. The research method restructures the integrated classification of 32 industries into 34, including the digital bio-healthcare industry, using the classification criteria of the government and professional institutions, and then reorganizes the digital bio-healthcare industry into eight industries classified as one industry group. The analysis data was taken from the Bank of Korea s 2019 data. Various trigger coefficients and ripple effects coefficients were rewritten using the analysis method of the Input-output Statistics. The analysis of the results compares the employment-induced effects of the digital bio-healthcare industry and the ripple effects of related industries in production, investment and value-added. In addition, in terms of investment effect, the effects of in-house and related industries were compared. It is hoped that the results of this study will be used to establish employment and industrial policies.
Jeong, Kwang-Un,Jang, Ji-Hyun,Kim, Dae-Yoon,Nah, Changwoon,Lee, Joong Hee,Lee, Myong-Hoon,Sun, Hao-Jan,Wang, Chien-Lung,Cheng, Stephen Z. D.,Thomas, Edwin L. Royal Society of Chemistry 2011 Journal of materials chemistry Vol.21 No.19
<P>Combining the physical principle of actuators with the basic concept of photonic crystals, colour-tunable three-dimensional (3D) photonic actuators were successfully fabricated. By controlling the <I>d</I>-spacings and the refractive index contrasts of the self-assembled 3D colloidal photonic crystals, colours of the photonic actuators were tuned. Various shapes of these 3D actuating objects were constructed by transforming the programmed 2D structures <I>via</I> bending, twisting and folding mechanisms. These 2D structures were first programmed by breaking the symmetry. The selective swellings were then applied as driving forces to control the shapes and colours of the photonic actuators. Scroll photonic actuators had been first demonstrated by bending the traditional 2D cantilever structure (K.-U. Jeong, <I>et al.</I>, <I>J.</I><I>Mater.</I><I>Chem.</I>, 2009, <B>19</B>, 1956). By breaking the symmetry of a cantilever structure perpendicular to its long axis, polypeptide-/DNA-like 3D helical photonic actuators were obtained from the programmed 2D structure <I>via</I> twisting processes. Both left- and right-handed scrolls and helices with various colours can be achieved by changing the polarity of solvents. Different types of 3D actuators, such as cube, pyramid and phlat ball, were also demonstrated <I>via</I> the folding mechanism. The reversible 3D photonic actuators transformed from the programmed 2D structures <I>via</I> the bending, twisting and folding mechanisms may be applied in the field of mechanical actuators, and optoelectronic and bio-mimetic devices.</P> <P>Graphic Abstract</P><P>Reversible colour and shape tunable photonic actuators were constructed by transforming the programmed 2D structures to the 3D objects <I>via</I> bending, twisting and folding mechanisms. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0jm03631e'> </P>
Colour-tunable spiral photonic actuators
Jeong, Kwang-Un,Jang, Ji-Hyun,Koh, Cheong Yang,Graham, Matthew J.,Jin, Kwang-Yong,Park, Soo-Jin,Nah, Changwoon,Lee, Myong-Hoon,Cheng, Stephen Z. D.,Thomas, Edwin L. Royal Society of Chemistry 2009 Journal of materials chemistry Vol.19 No.14
<P>Combining the multi-faceted environmental responsiveness of polymers with photonically active structures, we developed spiral photonic actuators which can reversibly change both shape and colour in response to the chemical environment.</P> <P>Graphic Abstract</P><P>Combining the multi-faceted environmental responsiveness of polymers with photonically active structures, we developed spiral photonic actuators which can reversibly change both shape and colour in response to the chemical environment. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b822980p'> </P>
( Minsu Lee ),( Junghyun Lee ),( Jihye Jang ),( Changwoon Nah ),( Yang-il Huh ) 한국고무학회 2019 엘라스토머 및 콤포지트 Vol.54 No.4
Poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels modified with various co-monomers, such as N-vinyl pyrrolidone (NVP), glycidyl methacrylate (GMA), and glycerol monomethacrylate (GMMA), were prepared to investigate the effect of adding a co-monomer on the water contents, surface wettability, and tensile modulus. These polymers were synthesized by thermal- and photo-polymerization in the presence of azobisisobutyronitrile (AIBN) and diphenyl(2,4,6- trimethylbenzoyl)-phosphineoxide (TPO) as the initiators. The characteristics of the hydrogels were analyzed via FTIR and UV/Vis spectroscopies, contact angle measurements, and tensile modulus measurements with UTM. Regarding the properties of water in the hydrogels, the ratio between free to bound water was investigated using differential scanning calorimetry (DSC). The effects of adding the co-monomers on the water content, surface wettability, and tensile modulus for soft contact lenses were also investigated. In the case of p(HEMA-co-NVP) hydrogels, the increase in the equilibrium water content (EWC) was primarily due to the increase in the bound water content. For p(HEMA-co-GMMA) hydrogels, an increase in free water content was the main reason for the increased EWC. In contrast, in the case of p(HEMA-co-GMA) hydrogels, a decrease in bound water content was observed to be the main factor that reduced the EWC. Photo-polymerized PHEMA hydrogels showed enhanced surface wettability and tensile modulus as compared to those produced via thermal polymerization.
박용민(Yongmin Park),황태경(Tae Kyung Hwang ),정상기(Sangki Chung),박노현(Nohyun Park),장준열(Jun Yeol Jang),나창운(Changwoon Nah) 한국추진공학회 2017 한국추진공학회지 Vol.21 No.2
Tow Prepreg is the intermediate material for filament winding process that has been “pre-impregnated fiber tow” with resin system. As “dry filament winding” process emerges as a reliable alternative to conventional filament winding (called “wet filament winding”) process, interest in tow prepreg as a material for dry filament winding is rising as well. In this article, we have reviewed the recent research trends in carbon fiber tow prepreg for high-performance rocket motor cases, fuel tanks for hydrogen vehicles and other high-quality commercial pressure vessels.