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Junyeong Kim,Kug-Hwan Kim,Dongil Kwon 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.2
Since materials used in or exposed to high-temperature environments can undergo variation or degradation of mechanical properties, it is important to evaluate mechanical properties at high temperature, in particular for structural applications and aerospace materials. Instrumented indentation testing (IIT) is widely used to evaluate such mechanical properties of materials as tensile properties, residual stress, fracture toughness, etc., exploiting theoretical approaches to indentation mechanics. In this study, we used IIT to evaluate variations in tensile properties with temperature of the Ti alloy Ti-6Al-4V, a candidate material for aerospace applications, using a high-temperature chamber and a modified representation method. Comparison of our results with conventional uniaxial tensile test results showed good agreement (within a 10% error range) in yield strength and ultimate tensile strength. This confirms the potential of IIT for evaluating to evaluate high-temperature tensile properties of metallic materials and for research on material behavior in various temperature conditions.
Kim, Doyeon,Lee, Geumbee,Kim, Daeil,Yun, Junyeong,Lee, Sang-Soo,Ha, Jeong Sook The Royal Society of Chemistry 2016 Nanoscale Vol.8 No.34
<P>In this study, we report the fabrication of a high performance flexible micro-supercapacitor (MSC) with an organic gel electrolyte containing a redox-active additive, referred to as poly(methyl methacrylate)-propylene carbonate-lithium perchlorate-hydroquinone (PMMA-PC-LiClO4-HQ). Hexagonal MSCs fabricated on thin polyethylene terephthalate (PET) films had interdigitated electrodes made of spray-coated multi-walled carbon nanotubes (MWNTs) on Au. The addition of HQ as a redox-active additive enhanced not only the specific capacitance but also the energy density of the MSCs dramatically, which is approximately 35 times higher than that of MSCs without the HQ additive. In addition, both areal capacitance and areal energy density could be doubled by fabrication of double-sided MSCs, where two MSCs are connected in parallel. The double-sided MSCs exhibited stable electrochemical performance during repeated deformation by bending. By dry-transferring the double-sided MSCs based on PMMA-PC-LiClO4-HQ on a deformable polymer substrate, we fabricated a stretchable MSC array, which also retained its electrochemical performance during a uniaxial strain of 40%. Furthermore, a wearable energy storage bracelet made of such an MSC array could operate a mu-LED on the wrist.</P>
Genome-resolved metagenomics: a game changer for microbiome medicine
Kim Nayeon,Ma Junyeong,Kim Wonjong,Kim Jungyeon,Belenky Peter,Lee Insuk 생화학분자생물학회 2024 Experimental and molecular medicine Vol.56 No.-
Recent substantial evidence implicating commensal bacteria in human diseases has given rise to a new domain in biomedical research: microbiome medicine. This emerging field aims to understand and leverage the human microbiota and derivative molecules for disease prevention and treatment. Despite the complex and hierarchical organization of this ecosystem, most research over the years has relied on 16S amplicon sequencing, a legacy of bacterial phylogeny and taxonomy. Although advanced sequencing technologies have enabled cost-effective analysis of entire microbiota, translating the relatively short nucleotide information into the functional and taxonomic organization of the microbiome has posed challenges until recently. In the last decade, genome-resolved metagenomics, which aims to reconstruct microbial genomes directly from whole-metagenome sequencing data, has made significant strides and continues to unveil the mysteries of various human-associated microbial communities. There has been a rapid increase in the volume of whole metagenome sequencing data and in the compilation of novel metagenome-assembled genomes and protein sequences in public depositories. This review provides an overview of the capabilities and methods of genome-resolved metagenomics for studying the human microbiome, with a focus on investigating the prokaryotic microbiota of the human gut. Just as decoding the human genome and its variations marked the beginning of the genomic medicine era, unraveling the genomes of commensal microbes and their sequence variations is ushering us into the era of microbiome medicine. Genome-resolved metagenomics stands as a pivotal tool in this transition and can accelerate our journey toward achieving these scientific and medical milestones.
Adsorption/desorption behavior of carbonyl sulfide gas on Scheelite type MWO<sub>4</sub> adsorbent
Kim, Junyeong,Do, Jeong Yeon,Park, No-Kuk,Hong, Jin-Pyo,Kang, Misook Elsevier 2018 Separation and purification technology Vol.207 No.-
<P><B>Abstract</B></P> <P>This study focused the metal oxide adsorbents to remove small amounts of carbonyl sulfide (OCS) during coal gasification, which was a preliminary step for Integrated Gasification Fuel Cell operation. This study attempted to improve the function of the adsorbent by introducing two kinds of metal species, alkaline earth metals (M=Ca, Mg, Sr, and Ba) and W, fabricated as a Scheelite-typed MWO<SUB>4</SUB> crystal. COS gases were broken down into CO and S segments on the surface of the adsorbents, and were then adsorbed onto the alkaline and W sides. The COS removals decreased in the order of CaWO<SUB>4</SUB> > SrWO<SUB>4</SUB> > BaWO<SUB>4</SUB> > MgWO<SUB>4</SUB> > WO<SUB>3</SUB>. When the adsorbent had an ideal basicity, the CO and S adsorbed well on the surface of the adsorbent, resulting in easy breakage of the CO and S bonds. But, this study indicated that it was more influential to optimally align the adsorbate and adsorbent surface. For the Scheelite-type CaWO<SUB>4</SUB> adsorbent, the distance of the adsorbing active site, CaOW, was similar in size to the COS adsorbate molecule, suggested a good alignment approaching the <I>C</I>-axis of the adsorbent. Moreover, an important result in this study determined by mass spectroscopy was that when COS adsorption was saturated on the MWO<SUB>4</SUB> surface, the adsorbed COS gases could desorb from the MWO<SUB>4</SUB> surface with CO<SUB>2</SUB>, SO<SUB>2</SUB>, CS, and CS<SUB>2</SUB> gases, which are more toxic than COS. This can be considered to other secondary environmental pollutants.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Scheelite-typed MWO<SUB>4</SUB> crystals fabricated by alkaline earth metals and W. </LI> <LI> COS molecules were broken down into CO and S segments on adsorbents. </LI> <LI> COS removal ability was the best on CaWO<SUB>4</SUB> adsorbent. </LI> <LI> On CaWO<SUB>4</SUB>, the COS adsorbate had a good alignment approaches forward the <I>C</I>-axis of the adsorbent. </LI> <LI> COS gases were desorbed as CO<SUB>2</SUB>, SO<SUB>2</SUB>, CS, and CS<SUB>2</SUB> gases. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kim, Daehee,An, Junyeong,Kim, Bongkyu,Jang, Jae Kyung,Kim, Byung Hong,Chang, In Seop Wiley-VCH 2012 CHEM SUS CHEM Vol.5 No.6
<P>To scale-up microbial fuel cells (MFCs), installing multiple unit cells in a common reactor has been proposed; however, there has been a serious potential drop when connecting unit cells in series. To determine the source of the loss, a basic stack-MFC (BS-MFC) has been devised, and the results show that the phenomenon is due to ions on the anode electrode traveling through the electrolyte to be reduced at the cathode connected in series. As calculated by means of the percentage potential drop, the degree of potential drop decreased with an increase in the unit-cell distance. When the distance was increased from 1 to 8 cm, the percentage potential drop in BS-MFC1 decreased from 46.76 ± 0.90 to 45.08 ± 0.70 % and in BS-MFC2 from 46.41 ± 0.95 to 43.82 ± 2.23 %. As the p-value of the t-test was lower than 0.05, the difference was considered significant; however, if the unit cells are installed far enough from each other to avoid the potential drop phenomenon, the system will be less dense, consequently reducing the ratio of electrode area per volume of anode compartment and decreasing the power density of the system. Finally, this study suggests design criteria for scaling-up MFC systems: Multiple-electrode-installed MFCs are modularized, and the unit cells are connected in series across the module (connecting each unit cell does not share the anolyte).</P>