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Carbon/epoxy composite foot structure for biped robots
Lee, Jinyi,Lee, Dongyoung,Park, Jongwon,Choi, Ilbeom,Lim, Jun Woo,Kim, Soohyun,Lee, Dai Gil Elsevier 2016 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.140 No.-
<P><B>Abstract</B></P> <P>Although aluminum structures are generally used for robot structures due to their high specific strength, aluminum feet for fast running biped robots are vulnerable to fatigue failure due to the low fatigue limit and low vibration damping of aluminum structures under repeated impact loadings on the feet. On the other hand, carbon/epoxy composites not only have a much higher specific fatigue limit but also have a higher material damping than that of aluminum.</P> <P>In this study, a carbon/epoxy composite foot structure of a biped robot was developed. The composite foot structure was designed for optimum performances such as weight saving, natural frequency, damping, and compliance for vibration isolation. Then its performances were analytically and experimentally obtained and compared with those of an aluminum foot structure. Finally, an optimum configuration of the composite foot structure was suggested for the reliable dynamic performance of the biped robot.</P>
Replitase - associated Enzyme Activities and Their Allosteric Interactions
Lee, Jung eun,Park, Sang Dai,Shim, Eun Yong,Kim, Chang Gil 한국유전학회 1990 Genes & Genomics Vol.12 No.4
A multienzyme complex responsible for DNA replication was isolated from the nuclei of synchronized LP1-1 cells, in which LMTK^- cell was transfected with Herpes simplex viral thymidine kinase gene (HSVTK). The nuclear fraction was found to contain spherical particles of ranging from 33.7 to 50.6 ㎚ in diameter, apparently multienzyme complex for de novo DNA biosynthesis. This multienzyme complex, termed as 'replitase', had several enzyme activities of DNA polymerase α, protein kinase, thymidine kinase and topoisomerase II, and thus, could catalyse the incorporation of labelled precursors into DNA. DNA polymerase α and its associated enzyme activities were unique to cells in S phase and increased coordinately during the G1/S phase transition of the cell cycle, suggesting the functional association of thymidine kinase with DNA polymerase α at the levels of multienzyme complex and nuclear matrix. Hydroxyurea, aphidicolin and novobiocin, inhibitors of ribonucleotide reductase, DNA polymerase α and δ, and topoisomerase, respectively, all inhibited thymidine kinase and DNA polymerase α activities in intact S phase LP1-1 cells. However, in permeabilized cells hydroxyurea had no inhibitory effect on the activity of either enzyme, while aphidicolin, novobiocin and TK antiserum inhibited the activities of thymidine kinase and DNA polymerase α. The similar inhibitions observed in permeabilized cells were seen in the preparations of multienzyme complex and nuclear matrix. These results support the hypothesis that transfected viral thymidine kinase acts as a component of the multienzyme complex responsible for DNA replication and has an allosteric interaction with the subunits of the multienzyme complex.
Development of non-woven carbon felt composite bipolar plates using the soft layer method
Lee, Dongyoung,Choe, Jaeheon,Nam, Soohyun,Lim, Jun Woo,Choi, Ilbeom,Lee, Dai Gil ELSEVIER (APPLIED SCIENCE) 2017 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.160 No.-
<P><B>Abstract</B></P> <P>Carbon fiber reinforced polymer composites are ideal substitutes for brittle graphite for electrically conductive bipolar plates because of their high mechanical property and productivity. Early composite bipolar plates suffered from high electrical contact resistance due to the resin-rich area formed on the surface. To decrease the electrical contact resistance, the “soft layer method” was developed, which exposed bare carbon fibers on the composite surface. This method significantly improved the electrical as well as mechanical properties of composite bipolar plates. The remaining problem for wider commercialization of composite bipolar plates is their high fabrication pressure.</P> <P>In this work, a non-woven carbon felt composite bipolar plate was developed to obtain improved electrical properties with low fabrication pressure. The soft layer method was also used to expose bare carbon fibers. Compared to conventional high fiber volume fraction composite bipolar plates, the developed bipolar plate exhibited superior electrical properties.</P>
Electro-mechanical properties of the carbon fabric composites with fibers exposed on the surface
Lee, Dongyoung,Lee, Dai Gil Elsevier 2016 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.140 No.-
<P><B>Abstract</B></P> <P>The carbon/epoxy composite is an ideal substitute for the brittle graphite bipolar plate of the proton exchange membrane fuel cell (PEMFC) because of its high mechanical property and productivity. However, composite bipolar plate suffered from high electrical contact resistance due to the resin-rich area formed on the surface. In order to decrease the contact resistance, “soft layer method”, which could expose bare carbon fibers on the composite surface, was developed. The soft layer method significantly improved the electrical properties of the unidirectional continuous carbon fiber/epoxy composite at the expense of slight degradation of the mechanical properties.</P> <P>In this work, the soft layer method was improved further to develop the carbon fabric/epoxy composite bipolar plate for the PEMFC. Compared to the conventional composite bipolar plates, the developed composite bipolar plates showed superior electrical properties as well as significant increase in the mechanical properties and gas tightness.</P>
Lee, Kwan Ho,Kim, Byoung Jung,Yoon, Soon Ho,Lee, Dai Gil Informa UK (TaylorFrancis) 2009 Journal of adhesion science and technology Vol.23 No.4
<P>Since metal foils such as aluminum, copper or nickel foils have been used in composite structures for radiation shielding and EMI protection in space environments, high adhesive bonding strength and durability between metal foils and composites under large temperature variations are very important. In this study, the strength of co-cure bonded joint between an aluminum foil and a composite has been investigated, with three different aluminum surface treatments such as standard PAA (Phosphoric Acid Anodization) procedure, abrasion with sandpaper, and carbon black pasting on the metal foils. From the double cantilever beam (DCB) tests, it was found that the interlaminar peel strength with carbon black pasting improved 60% compared to the laminate without any surface treatment. Also it was found that the interlaminar peel strength of the co-cure carbon/epoxy composite-aluminum foil hybrid laminate with the carbon black pasting on the aluminum foil did not decrease after many thermal cycles from 30°C to −196°C.</P>