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Jeonju, South Korea

Chonbuk National University is a national research university founded in 1947, located in Jeonju, South Korea. As the flagship national university for the Jeollabuk-do province , Chonbuk National University has been ranked 501–550th in the world by QS Top Universities Ranking in 2010. Wikipedia.

Choi W.-Y.,Chonbuk National University
IEEE Transactions on Power Electronics | Year: 2013

This paper proposes a high-efficiency dc-dc converter with fast dynamic response for low-voltage photovoltaic (PV) sources. The voltage stress of power switches is reduced at low-voltage side. Zero-current turn-off of output diodes is achieved at high-voltage side. Power efficiency is improved by reducing switching power losses. A modified proportional and integral controller is also suggested to achieve fast output voltage control. The dynamic response of the proposed converter is improved. The performance of the proposed converter is verified based on an experimental prototype for a 200-W PV module. © 1986-2012 IEEE. Source

Lee S.J.,Chonbuk National University | Michel S.L.J.,University of Maryland, Baltimore
Accounts of Chemical Research | Year: 2014

ConspectusZinc finger (ZF) proteins are a large family of metalloproteins that utilize zinc for structural purposes. Zinc coordinates to a combination of cysteine thiol and histidine imidazole residues within the ZF polypeptide sequence resulting in a folded and functional protein. Initially, a single class of ZFs were identified. These ZFs, now referred to as the "classical" ZFs, utilize a Cys2His2 (CCHH) ligand set to bind zinc. Upon Zn coordination, the classical ZFs fold into a structure made up of an α helix and an antiparallel β sheet. When folded, classical ZFs recognize and bind to specific DNA targets and function as transcription factors. With the advent of genome sequencing and proteomics, many additional classes of ZFs were identified based upon their primary amino acid sequences. At least 13 additional classes of ZFs are known, and collectively these "nonclassical" ZFs differ in the ligand set involved in Zn(II) coordination, the organization of the ligands within the polypeptide sequence and the macromolecular targets. Some nonclassical ZFs are DNA binding "transcription factors", while others are involved in RNA regulation and protein recognition. Much less is known about these nonclassical ZFs with regards to the roles of metal coordination in fold and function. This Account focuses on our laboratorys efforts to characterize two families of "nonclassical" ZFs: the Cys3His (or CCCH) ZF family and the Cys2His2Cys (or CCHHC) ZF family.Our work on the CCCH ZF family has focused on the protein Tristetraprolin (TTP), which is a key protein in regulating inflammation. TTP contains two CCCH domains that were proposed to be ZFs based upon their sequence. We have shown that while this protein can coordinate Zn(II) at the CCCH sites, it can also coordinate Fe(II) and Fe(III). Moreover, the zinc and iron bound forms of TTP are equally adept at discriminating between RNA targets, which we have demonstrated via a fluorescence anisotropy based approach. Thus, CCCH type ZFs appear to be promiscuous with respect to metal preference and a role for iron coordination in CCCH ZF function is proposed.The CCHHC family of ZFs is a small family of nonclassical ZFs that are essential for the development of the central nervous system. There are three ZFs in this family: neural zinc finger factor-1 (NZF-1), myelin transcription factor-1 (MyT1), and suppressor of tumorgenicity 18 (ST18). All three proteins contain multiple clusters of "CCHHC" domains, which are all predicted to be Zn binding domains. We have focused on a tandem-CCHHC domain construct of NZF-1, which recognizes β-RARE DNA, and we have identified key residues required for DNA recognition. Unlike classical ZFs, for which a few conserved residues are required for DNA recognition, the CCHHC class of ZFs utilize a few nonconserved residues to drive DNA recognition leading us to propose a new paradigm for ZF/DNA binding. © 2014 American Chemical Society. Source

Shon I.-J.,Chonbuk National University
Journal of Korean Institute of Metals and Materials | Year: 2014

Pulsed current activated sintering and spark plasma sintering enhance sinter-ability, The advantage of these processes is that they allow very quick densification to near theoretical density and inhibition of grain growth. Highly dense nanostructured intermetallic compounds, oxides, metal-ceramic composites, high temperature materials and hard materials were produced with a simultaneous application of pressure and a pulsed current within several minutes. The role of the current in sintering or synthesis has been the focus of several studies aimed at explaining enhanced sintering and improved properties. The role played by the current has had various interpretations, with the effect explained in terms of the fast heating rate due to Joule heating, the presence of plasma in pores separating powder particles, and the intrinsic contribution of the current to mass transport. Copyright © The Korean Institute of Metals and Materials. Source

Hong H.,Chonbuk National University | Strogatz S.H.,Cornell University
Physical Review Letters | Year: 2011

We consider a generalization of the Kuramoto model in which the oscillators are coupled to the mean field with random signs. Oscillators with positive coupling are "conformists"; they are attracted to the mean field and tend to synchronize with it. Oscillators with negative coupling are "contrarians"; they are repelled by the mean field and prefer a phase diametrically opposed to it. The model is simple and exactly solvable, yet some of its behavior is surprising. Along with the stationary states one might have expected (a desynchronized state, and a partially-synchronized state, with conformists and contrarians locked in antiphase), it also displays a traveling wave, in which the mean field oscillates at a frequency different from the population's mean natural frequency. © 2011 American Physical Society. Source

Kwon S.-D.,Chonbuk National University
Applied Physics Letters | Year: 2010

This paper proposes a T-shaped piezoelectric cantilever for generating electric power from fluid flow. The working principle of the device is based on aeroelastic flutter and utilizes a bimorph cantilever with T-shape which hastens occurrence of flutter at a low fluid speed. A prototype device (100×60×30 mm3) was tested in a wind tunnel. The device was found to provide power from a wind speed of 4 m/s and a continuous peak electrical power output of 4.0 mW. The simplicity of the present device consisting of only a bimorph cantilever is considered to be cost effective. © 2010 American Institute of Physics. Source

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