RandD Center

Seoul, South Korea

RandD Center

Seoul, South Korea

Time filter

Source Type

Jeong M.S.,Sungkyunkwan University | Han J.H.,Chonnam National University | Choi Y.C.,RandD Center
Carbon | Year: 2013

Single-walled carbon nanotubes (SWCNTs) were synthesized by arc discharge and then purified by a two-step process including thermal and acid treatments. As-synthesized, thermal-treated, and fully purified (thermal- and acid-treated) samples were characterized using thermogravimetric analysis, continuous resonant Raman scattering, and ultraviolet-visible-near infrared (UV-Vis-NIR) absorption spectroscopy. Thermal and acid treatments eliminate carbonaceous particles and metal catalyst particles, respectively, resulting in high-purity SWCNTs. Continuous resonant Raman scattering and UV-Vis-NIR absorption spectroscopy demonstrated that the metallic content of the arc-synthesized SWCNTs varied according to the purification process; as-synthesized (∼15%), thermal-treated (∼30%), and thermal/acid-treated (∼25%). Transparent conducting films were prepared using three different purity grades and their properties were analyzed. Thermal-treated nanotubes displayed superior performance compared with the other samples owing to its higher metallic content and smaller bundle diameters. © 2013 Elsevier Ltd. All rights reserved.

Jin Y.G.,Korea Atomic Energy Research Institute | Baek H.M.,KAIST | Hwang S.K.,KAIST | Im Y.-T.,KAIST | Jeon B.C.,RandD Center
Journal of Materials Processing Technology | Year: 2012

Aluminum alloy 6061-T6 was used to produce an ultrafine-grained specimen by spring-loaded equal channel angular pressing (ECAP), which was continuously applied to a commercial multi-stage former at a production rate of 30 rpm at room temperature to manufacture high strength aluminum bolts. In order to increase the mechanical strength of the manufactured bolt, the bolt-forming process was introduced based on extrusion process in the present work. With the specimens processed by a single pass ECAP, underfilling at the bolt head and surface cracking at the flange of the produced bolts were observed due to the geometry of the ECAPed specimen and friction at the die interface, respectively. To remove these defects, modified route C for the second pass ECAP and aluminum fluoride coating with metal soap for the initial specimen were applied. Finally, the ultrafine-grained aluminum bolts were successfully manufactured in a continuous sequence. Both the ultimate tensile strength (UTS) and elongation to fracture of the manufactured bolts increased compared to the conventionally made bolts. According to the present investigation, an innovative approach utilizing the ECAP to develop high strength bolts without modifying conventional material is demonstrated. © 2011 Elsevier B.V. All rights reserved.

Yoon D.-H.,Yeungnam University | Choi Y.C.,RandD Center
Current Applied Physics | Year: 2013

Stable and uniform electron field emitters were fabricated by the screen-printing of a carbon nanotube (CNT) paste. The CNT paste was prepared by mixing thin multi-walled CNTs, organic binder and glass frits in terpineol followed by three-roll milling. The paste was screen-printed onto an indium tin oxide (ITO)-coated glass substrate and exposed to firing. The emitters formed by the adhesive tape treatment of the printed pastes generally showed non-uniform heights of emitting tips due to the large-sized glass frit distributed in the paste. On the other hand, small glass frits with a uniform particle size distribution could be obtained by high energy milling. In addition, the CNT paste prepared using the high energymilled glass frits showed very uniform tip heights. The uniform CNT tip height was found to play an important role in acquiring the long-term emission stability and uniformity of field emitters. © 2013 Elsevier B.V. All rights reserved.

Atanasova J.,RandD Center | Ivanova I.,Sofia University
Biotechnology and Biotechnological Equipment | Year: 2010

Milk is an excellent source of well balanced nutrients and also exhibits a range of biological activities that influence digestion, metabolic responses to absorbed nutrients, growth and development of specific organs, and resistance to disease. Goat milk is as close to perfect food as possible in nature. Bioactive peptides have been defined as specific protein fragments that have a positive impact on body functions or conditions and may ultimately influence health. It can be generated during milk fermentation by the proteolytic activity of starter cultures. The beneficial health effects may be classified as antimicrobial, antioxidative, antithrombotic, antihypertensive and immunomodulatory. Sheep and goat milk proteins are also important sources of bioactive ACE inhibitory peptides and antihypertensive peptides. They can provide a non- immune disease defence and control of microbial infections. The activity of these biofunctional peptides is based on their inherent amino acid composition and sequence. The size of active sequences may vary from two to twenty amino acid residues. The total antibacterial effect in milk is greater than the sum of the individual contributions of immunoglobulin and nonimmunoglobulin defence proteins such as LF, LP, lysozyme, and other peptides. A variety of naturally formed bioactive peptides have been found in fermented dairy products, such as yoghurt, sour milk and cheese. BP have the potential to be used in the formulation of health-enhancing nutraceuticals, and as potent drugs with well defined pharmacological effects.

Kim J.S.,RandD Center | Cho S.J.,RandD Center | Jeong K.S.,RandD Center | Choi Y.C.,RandD Center | Jeong M.S.,Gwangju Institute of Science and Technology
Carbon | Year: 2011

Very long and highly dispersible multi-walled carbon nanotube (MWCNT) bundles were synthesized in large quantity by catalytic chemical vapor deposition, and their structural and electrical properties were characterized. It was found that the MWCNTs could be synthesized with either bundled (long-aligned) or short-entangled structure depending on the catalyst system. The aligned MWCNTs were found to be more conductive and more dispersible than the entangled ones. The MWCNT/poly (methyl methacrylate) composites were prepared using both entangled and aligned MWCNTs. The aligned MWCNTs were found to give the composite higher electrical conductivity, which might be attributed to long length and high dispersibility. It was further found that the longer the MWCNT bundle, the higher electrical conductivity of the composite. © 2011 Elsevier Ltd. All rights reserved.

Lee S.W.R.,RandD Center
Proceedings of Technical Papers - International Microsystems, Packaging, Assembly, and Circuits Technology Conference, IMPACT | Year: 2011

Currently most LED components are made with individual chip packaging technology. The main manufacturing processes follow conventional chip-based IC packaging. In the past several years, there is an uprising trend in the IC industry to migrate from chip-based packaging to wafer level packaging. Therefore, there is a need for LEDs to catch up. This presentation will introduce advanced LED wafer level packaging technologies. The contents will cover key enabling processes such as preparation of silicon sub-mount wafer, implementation of interconnection, deposition of phosphor, wafer level encapsulation, and their integration. The emphasis will be placed on how to achieve high throughput, low cost manufacturing through wafer level packaging. © 2011 IEEE.

Lee B.,RandD Center | Yoon J.R.,RandD Center
Electronic Materials Letters | Year: 2013

In this work, granule Li4Ti5O12 was successfully synthesized by spray drying a precursor slurry, followed by the solid-state reaction method. The precursor slurry was prepared from a solution of lithium carbonate (Li2CO3) and titanium dioxide (TiO2) in deionized water. A hybrid capacitor was fabricated which comprised a granule Li4Ti5O12 anode and activated carbon cathode. For comparison, an electrical double-layer capacitor (EDLC) cell was fabricated by using activated carbon electrodes in the same way. The electrochemical performance of the hybrid capacitor and the EDLC was characterized by constant current charge/discharge curves and cycle performance testing. The electrochemical testing results showed that the capacitance of the hybrid capacitor is approximately 2.5 times higher than that of the EDLC. Furthermore, the capacitance of the EDLC and the hybrid capacitor barely decreased after 1,000 cycles. The results of this study demonstrate that the hybrid capacitor has the advantages of the high rate capability of a supercapacitor (EDLC) and high battery capacity. © 2013 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.

Lim G.,Kyung Hee University | Hwang H.J.,RandD Center | Kim J.H.,Kyung Hee University
Analytical Biochemistry | Year: 2011

A new efficient immobilization method that enables oriented immobilization of biologically active proteins was developed based on concepts of active site masking and kinetic control. Taq DNA polymerase was immobilized covalently on mixed self-assembled monolayers (SAMs) of ω-carboxylated thiol and ω-hydroxylated thiol through amide bonds between the protein and the carboxyl group in SAMs. Activity of the immobilized enzyme as large as 70% of solution-phase enzyme was achieved by masking the active site of the Taq DNA polymerase prior to the immobilization. In addition, the number of immobilization bonds was controlled by optimizing the carboxyl group concentration in the mixed monolayer. The maximum activity of immobilized Taq DNA polymerase was achieved at 5% of 12-mercaptododecanoic acid. The activity observed with protected immobilized enzyme was approximately 20 times higher than that observed with randomly immobilized enzyme. The maximum activity was acquired at a 1:1 DNA/enzyme masking ratio, immobilization pH 8.3, and within 10 min of reaction time. This concept of the active site masking and kinetic control of the number of covalent bonds between proteins and the surface can be generally applicable to a broad range of proteins to be immobilized on the solid surface with higher activity. © 2011 Elsevier Inc. All rights reserved.

Lee Y.,Yonsei University | Shin Y.J.,RandD Center | Ahn S.K.,Incheon National University
Bioorganic and Medicinal Chemistry Letters | Year: 2014

Many adamantane derivatives have been demonstrated to function as 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) inhibitors. 3-Amino-N-adamantyl-3-methylbutanamide derivatives were optimized by structure-based drug design. Compound 8j exhibited a good in vitro and ex vivo inhibitory activity against both human and mouse 11β-HSD1. © 2014 Elsevier Ltd. All rights reserved.

Lee B.,RandD Center | Yoon J.R.,RandD Center
Current Applied Physics | Year: 2013

Spinel-Li4Ti5O12 is successfully synthesized by a solid phase synthesis. The Li4Ti5O 12 powders with various dopants (Al3+, Cr3+, Mg2+) synthesized at 800°C are in accordance with the Li 4Ti5O12 cubic spinel phase structure. The dopants are inserted into the lattice structure of Li4Ti 5O12 without causing any changes in structural characteristics. In order to study the effect on various dopants, the hybrid supercapacitor is prepared by using un-doped Li4Ti5O 12 and doped Li4Ti5O12 in this work. The electrochemical performance of the hybrid supercapacitor is characterized by impedance spectroscopy and cycle performance. The results show Cr 3+ and Mg2+ dopants enhance the conductivity of Li 4Ti5O12. Also, Al3+ substitution improves the reversible capacity and cycling stability of Li4Ti 5O12. It is found that effect of dopant on the electrochemical performance of Li4Ti5O12 as electrode material for hybrid supercapacitor where the EDLC and the Li ion secondary battery coexist in one cell system. © 2013 Elsevier B.V. All rights reserved.

Loading RandD Center collaborators
Loading RandD Center collaborators