• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.37-52
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• 2013

무어의 법칙에 따르면, 반도체의 집적도 2년마다 2배씩 증가한다고 한다. 무어의 법칙은 지금까지는 집적회로 기술의 발전을 잘 예측했다. 하지만 트랜지스터의 사이즈를 줄일수록 누수전류와 회로의 저항을 조절하기 어렵기 때문에 트랜지스터의 소형화에는 한계가 있다. 우리는 곧 무어의 법칙의 한계를 맞이할 것이다. 그래서 트랜지스터를 더욱 소형화시키기 위해서는 bottom-up analysis가 필요한 시점이다. Top-down analysis가 초기의 커다란 트랜지스터에서 점점 소형화를 시켜 작은 트랜지스터를 만든다는 개념인 반면, Bottom-up analysis는 처음부터 작은 분자를 조작하여 트랜지스터와 같은 성질을 띄도록 만드는 개념이다. 분자가 기억소자로서 이용되려면 저항이 다른 2가지 안정한 상태가 필요하다. 이번 연구에서 나는 기억소자를 디자인 하기 위하여 high spin state와 low spin state 두 가지 안정한 상태를 가지는 spin crossover complex를 이용하기로 했다. 이전의 연구에서 spin crossover 는 전기장을 이용해서도 유도될 수 있다고 확신하였고, 이를 이용해서 기억소자를 디자인하기로 하였다. 이번 연구를 위해서 symmetry를 가지는 octahedral spin crossover complex를 디자인하였고 이를 '기억 분자'라고 명명했다. 그리고 이 분자의 high spin state와 low spin state가 전기장을 이용하여 서로 바뀔 수 있는지 가능성을 DFT with B3LYP functional을 이용해서 비교했다. 그 결과로 전기장을 이용하여 기억분자의 spin crossover을 일으킬 수는 있지만 abnormally strong electric field를 써야 한다는 사실을 알아냈다. 이번 연구를 토대로 추후의 연구를 위해, 기억소자가 되기 위하여 분자가 어떤 특징을 만족시켜야 하는지를 분석했다.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2835-2838
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• 2014

• Advances in nano research
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• v.13 no.3
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• pp.259-267
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• 2022

Two-dimensional (2D) transition metal carbides/nitrides or "MXenes" belong to a diverse-class of layered compounds, which offer composition- and electric-field-tunable electrical and physical properties. Although the majority of the MXenes, including Ti₃C₂T_x, are metallic, they typically show semiconductor-like behaviour in their percolated thin-film structure; this is also the most common structure used for fundamental studies and prototype device development of MXene. Magnetoconductance studies of thin-film MXenes are central to understanding their electronic transport properties and charge carrier dynamics, and also to evaluate their potential for spin-tronics and magnetoelectronics. Since MXenes are produced through solution processing, it is desirable to develop deposition strategies such as inkjet-printing to enable scale-up production with intricate structures/networks. Here, we systematically investigate the extrinsic negative magnetoconductance of inkjetprinted Ti₃C₂T_x MXene thin-films and report a crossover from weak anti-localization (WAL) to weak localization (WL) near 2.5K. The crossover from WAL to WL is consistent with strong, extrinsic, spin-orbit coupling, a key property for active control of spin currents in spin-orbitronic devices. From WAL/WL magnetoconductance analysis, we estimate that the printed MXene thin-film has a spin orbit coupling field of up to 0.84 T at 1.9 K. Our results and analyses offer a deeper understanding into microscopic charge carrier transport in Ti₃C₂T_x, revealing promising properties for printed, flexible, electronic and spinorbitronic device applications.

• Proceedings of the Korean Magnestics Society Conference
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• 2012.11a
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• pp.75-75
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• 2012

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.183-195
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• 2014

Kinetically constrained models (KCM) have attracted interest as models that assign dynamic origins to the interesting dynamic properties of supercooled liquid. Signs of dynamic heterogeneity in the crossover model that linearly interpolates between the FA-like symmetric constraint and the East model constraint by asymmetric parameter b were investigated using Monte Carlo technique. When the asymmetry parameter was decreased sufficiently, smooth fragile-to-strong dynamic transition was observed in terms of the relaxation time, diffusion constant, Stokes-Einstein violation, and dynamic length scale. Competition between energetically favored symmetric relaxation mechanism and entropically favored asymmetric relaxation mechanism is behind such transition.

• Bulletin of the Korean Chemical Society
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• v.29 no.6
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• pp.1233-1242
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• 2008

The hydration effect on the intrinsic magnetism of natural salmon double-strand DNA was explored using electron magnetic resonance (EMR) spectroscopy and superconducting quantum interference device (SQUID) magnetic measurements. We learned from this study that the magnetic properties of DNA are roughly classified into two distinct groups depending on their water content: One group is of higher water content in the range of 2.6-24 water molecules per nucleotide (wpn), where all the EMR parameters and SQUID susceptibilities are dominated by spin species experiencing quasi one-dimensional diffusive motion and are independent of the water content. The other group is of lower water content in the range of 1.4-0.5 wpn. In this group, the magnetic properties are most probably dominated by cyclotron motion of spin species along the helical π -way, which is possible when the momentum scattering time (${\tau}_k$) is long enough not only to satisfy the cyclotron resonance condition (${\omega}_c{\tau}_k$ > 1) but also to induce a constructive interference between the neighboring double helices. The same effect is reflected in the S-shaped magnetization-magnetic field strength (M-H) curves superimposed with the linear background obtained by SQUID measurements, which leads to larger susceptibilities at 1000 G when compared with the values at 10,000 G. In particular, we propose that the spin-orbital coupling and Faraday's mutual inductive effect can be utilized to interpret the dimensional crossover of spin motions from quasi 1D in the hydrate state to 3D in the dry state of dsDNA.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2505-2511
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• 2014

Indium oxide nanocrystals ($In_2O_3$ NCs) with sizes of 5.5 nm-10 nm were synthesized by hot injection of the mixture precursors, indium acetate and oleic acid, into alcohol solution (1-octadecanol and 1-octadecence mixture). Field emission transmission electron microscopy (FE-TEM), High resolution X-Ray diffraction (X-ray), Nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FT-IR) were employed to investigate the size, surface molecular structure, and crystallinity of the synthesized $In_2O_3$ NCs. When covered by oleic acid as a capping group, the $In_2O_3$ NCs had a high crystallinity with a cubic structure, demonstrating a narrow size distribution. A high mobility of $2.51cm^2/V{\cdot}s$ and an on/off current ratio of about $1.0{\times}10^3$ were observed with an $In_2O_3$ NCs thin film transistor (TFT) device, where the channel layer of $In_2O_3$ NCs thin films were formed by a solution process of spin coating, cured at a relatively low temperature, $350^{\circ}C$. A size-dependent, non-monotonic trend on electron mobility was distinctly observed: the electron mobility increased from $0.43cm^2/V{\cdot}s$ for NCs with a 5.5 nm diameter to $2.51cm^2/V{\cdot}s$ for NCs with a diameter of 7.1 nm, and then decreased for NCs larger than 7.1 nm. This phenomenon is clearly explained by the combination of a smaller number of hops, a decrease in charging energy, and a decrease in electronic coupling with the increasing NC size, where the crossover diameter is estimated to be 7.1 nm. The decrease in electronic coupling proved to be the decisive factor giving rise to the decrease in the mobility associated with increasing size in the larger NCs above the crossover diameter.

• Physical Therapy Rehabilitation Science
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• v.6 no.4
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• pp.189-195
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• 2017

Objective: The purpose of this study was to examine the effects of real-time visual feedback weight shift training during golf swinging on golf performance. Design: Repeated-measures crossover design. Methods: Twenty-sixth amateur golfers were enrolled and randomly divided into two groups: The golf swing training with real-time feedback on weight shift (experimental group) swing training on the Wii balance board (WBB) by viewing the center of pressure (COP) trajectory on the WBB. All participants were assigned to the experimental group and the control group. The general golf swing training group (control group) performed on the ground. The golf performance was measured using a high-speed 3-dimensional camera sensor which analyses the shot distance, ball velocity, vertical launch angle, horizontal launch angle, back spin velocity and side spin velocity. The COP trajectory was assessed during 10 practice sessions and the mean was used. The golf performance measurement was repeated three times and its mean value was used. The assessment and training were performed at 24-hour intervals. Results: After training sessions, the change in shot distance, ball velocity, and horizontal launch angle pre- and post-training were significantly different when using the driver and iron clubs in the experimental group (p<0.05). The interaction time${\times}$group and time${\times}$club were not significant for all variables. Conclusions: In this study, real-time feedback training using real-time feedback on weight shifting improves golf shot distance and accuracy, which will be effective in increasing golf performance. In addition, it can be used as an index for golf player ability.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.222-222
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• 1999

From extensive measurements of the resistance and the dynamic resistance as functions of magnetic field and temperature, we find that the transport in the insulating state beyond the superconductor-insulator (S-I) transition is dominated by bosons(Cooper pairs and/or vortices) and cannot be described by the theory of the fermionic insulating phase. The maximum of the magnetoresistance at B = B$_m$ and the following negative slope in R(B) with increasing field can be explained by the crossover from the "Bose-glass" to the "Fermi-glass" phase as suggested by Paalanen, Hebard, and Ruel. The zero bias peak in dv/dl for biases below the characteristic voltage V$_c$ (or current $I_c$), gives a clue for the assumption of the "dirty boson" model which states that the insulating state above the critical magnetic field is the phase where Cooper pairs are localized due to the Coulomb blockade with a nonvanishing order parameter. The shift to a lower value of the critical magnetic field by overlaying thin Au layer, which is known as a strong spin-orbit scatterer, also supports the bosonic nature of the S-I transition.