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Improvement of Magnetic Properties and Texture of FePt Thin Films on MgO Substrates by Sn Addition
DongWon Chun,SungMan Kim,GyeungHo Kim,WonYoung Jeung 한국자기학회 2009 Journal of Magnetics Vol.14 No.1
In this work, we studied the effects of Sn addition on the ordering temperature of FePt thin film. The coercivity of FePtSn film was about 1000 Oe greater than the coercivity of FePt film for an annealing temperature of 600℃. Therefore, Sn addition was effective in promoting the L1? ordering and in reducing the ordering temperature of the FePt film. From our X-ray diffraction results, we found that in the as-deposited film, the addition of Sn induced a lattice expansion in disordered FePt thin films. After the annealing process, the excess Sn diffuses out from the ordered FePt thin film because of the difference in the solid solubility of Sn between the disordered and ordered phases. The existence of precipitates of Sn from the FePt lattice was deduced by Curie temperature measurements of the FePt and FePtSn films. Therefore, the key role played by the addition of Sn to the FePt film can be explained by a reduction in the activation energy for the L10 order-disorder transformation of FePt which originates from the high internal stress in the disordered phase induced by the supersaturated Sn atoms.
The Effects of CrV Underlayer on the Structure and Magnetic Properties of FePt Thin Film
Chun, DongWon,Kim, SungMan,Kim, GyeungHo,Jeung, WonYoung IEEE 2010 IEEE transactions on magnetics Vol.46 No.6
<P> An attempt is made in this study to employ vanadium containing chromium (CrV) alloy underlayer to control the microstructure and ultimately to facilitate the <B><I>in-situ</I></B> ordering of Fe-Pt thin film. CrV alloys with V contents ranging from 0 to 15 at% were investigated to evaluate their effects on the magnetic properties and structural modification of FePt thin film. Addition of V in Cr underlayer results in the formation of FePt <TEX>${\rm L}1_{0}$</TEX> phase with (001) preferred orientation. Analysis of XRD and HR-TEM results reveals that the lattice expansion of Cr underlayer induced by V addition increases the lattice misfit strain between CrV underlayer and FePt magnetic layer. Consequently well aligned FePt (001) grains and <B><I>in-situ</I></B> ordering of FePt <TEX>${\rm L}1_{0}$</TEX> thin film can be obtained. Magnetic property measurements show that FePt/Pt/5.8 at.%V-Cr multilayer has the maximum out-of-plane coercivity (4000 Oe) and squareness (0.95). Due to <B><I>in-situ</I></B> ordering, good perpendicular magnetic properties with higher coercivity and squareness were achieved from <TEX>${\rm FePt/Pt/Cr}_{94.2}{\rm V}_{5.8}$</TEX> multi-layers at the processing temperature of 350<TEX>$^{\circ}{\rm C}$</TEX> without further annealing treatment. </P>
Identification of a novel signaling component in phosphate starvation responses from Arabidopsis
Hyun Jin Chun,Dongwon Baek,Cheol Woo Choi,Kyoung Hee Lee,Dae-Jin Yun,Min Chul Kim 한국육종학회 2012 한국육종학회 심포지엄 Vol.2012 No.07
Phosphorus is one of the macronutrients essential for plant growth and development, as well as crop productivity. Many soils around the world are deficient in phosphate (Pi) that plants can utilize. To cope with the stress of Pi starvation, plants have evolved many adaptive strategies, such as changes of root architecture and enhanced Pi acquisition form soil. To understand molecular mechanism underlying Pi starvation stress signaling, we characterized the activation-tagged mutant showing altered responses to Pi deficiency compared to wild type Arabidopsis and named hsp3 (hypersensitive to Pi starvation3). hsp3 mutant exhibits enhanced phosphate transporter activity, resulting in higher Pi content than wild type. However, in root architectural change under Pi starvation, hsp3 shows hyposensitive responses than wild type, such as longer primary root elongation, lower lateral root density. Histochemical analysis using hsp3 mutant expressing auxin-responsive DR5::GUS reporter gene, indicated that auxin allocation from primary to lateral roots under Pi starvation is aborted in hsp3 mutant. Molecular genetic analysis of hsp3 mutant revealed that the mutant phenotype is caused by the lesion in ENHANCED SILENCING PHENOTYPE4 (ESP4) gene whose function is proposed in mRNA 3’ end processing. Here, we propose that mRNA processing plays a crucial role in Pi homeostasis in Arabidopsis.
Cross-talk between Phosphate Starvation and Other Environmental Stress Signaling Pathways in Plants
Baek, Dongwon,Chun, Hyun Jin,Yun, Dae-Jin,Kim, Min Chul Korean Society for Molecular and Cellular Biology 2017 Molecules and cells Vol.40 No.10
The maintenance of inorganic phosphate (Pi) homeostasis is essential for plant growth and yield. Plants have evolved strategies to cope with Pi starvation at the transcriptional, post-transcriptional, and post-translational levels, which maximizes its availability. Many transcription factors, miRNAs, and transporters participate in the Pi starvation signaling pathway where their activities are modulated by sugar and phytohormone signaling. Environmental stresses significantly affect the uptake and utilization of nutrients by plants, but their effects on the Pi starvation response remain unclear. Recently, we reported that Pi starvation signaling is affected by abiotic stresses such as salt, abscisic acid, and drought. In this review, we identified transcription factors, such as MYB, WRKY, and zinc finger transcription factors with functions in Pi starvation and other environmental stress signaling. In silico analysis of the promoter regions of Pi starvation-responsive genes, including phosphate transporters, microRNAs, and phosphate starvation-induced genes, suggest that their expression may be regulated by other environmental stresses, such as hormones, drought, cold, heat, and pathogens as well as by Pi starvation. Thus, we suggest the possibility of cross-talk between Pi starvation signaling and other environmental stress signaling pathways.
최동원(Dongwon Choi),전용범(Youngbum Chun),박인송(Insong Park) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The position of the automobile head restraint is very important for the neck injury in the rear end collision. This study was analyzed about influence of the head restraint height and distance on neck injury during rear end collision. The effects of the position have been evaluated experimentally. The neck injuries are calculated by the relative acceleration between the upper and lower acceleration. A good head restraint position has been founded from analysis results based on the height covered head and the distance closed the back of the head. Also, a active head restraint is very useful for the neck injury.