• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.305-305
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• 2006

The molecular structure and dynamics of inclusion compounds (ICs) consisting of n-perfluoroalkane (PFA) guests and ${\Box}-cyclodextrin$ (${\Box}-CD$) host were investigated using $^{19}F$ magic angle spinning (MAS) and $^{1}H{\to}^{19}F$ cross polarization (CP) / MAS NMR spectroscopy with the aid of thermal analyses, FT-IR spectroscopy, X-ray diffraction, and $^{1}H{\to}^{19}F$ CP/MAS technique revealed that $C_{9}F_{20}$ molecules included in ${\Box}-CD$ undergo vigorous molecular motion and partly come out of the ${\Box}-CD$ channel above $80^{\circ}C$. In case of $C_{20}F_{42}/{\Box}-CD$, an exothermic peak is observed by differential scanning calorimetry (DSC) at ca. $40^{\circ}C$ which suggests that ${\Box}-CD$ molecules become mobile and commence rearrangements that form more ordered structures at higher temperatures.

• Journal of the Semiconductor & Display Technology
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• v.9 no.1
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• pp.1-4
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• 2010

We investigated a linear carbon nanotube motor serving as the key building block for nano-scale motion control by using molecular dynamics simulations. This linear nano-motor, is based on the electrostatically telescoping multi-walled carbon-nanotube with ultralow intershell sliding friction, is controlled by the gate potential with the capacitance feedback sensing. The resonant harmonic peaks are induced by the interference between the driving frequencies and its self-frequency. The temperature is very important factor to operate this nanomotor.

• Journal of the Korean Magnetic Resonance Society
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• v.5 no.2
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• pp.130-137
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• 2001

Backbone dynamics of the catalytic residues in free and steroid-bound $\Delta$$^{5}$ -3- ketosteroid isomerase from Pseudomonas testosteroni has been examined by $^{15}$ N relaxation measurements. The relaxation data were analyzed using the model-free formalism to extract the model-free parameters (S$^2$, $\tau$$_{e}$, and R$_{ex}$). Tyr-34 and Asp-99 exhibit enhanced high-frequency (pico- to nanosecond) internal motions in the free enzyme, which are restricted upon ligand binding, while Asp-38 experiences severe restriction of the internal motions in the fee enzyme, suggesting that Tyr-14 and Asp-99 are more actively involved in the ligand binding than Asp-38. The results also indicate that the H-bond network in the catalytic cavity might be slightly strengthened upon ligand binding, which may have some implications on the enzyme mechanism.he enzyme mechanism.m.

• Transactions of the Korean hydrogen and new energy society
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• v.12 no.3
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• pp.191-199
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• 2001

In this paper molecular dynamics simulations have been carried out to investigate energy and momentum transfer of hydrogen ions impacted on the Ni (100) surface with $45^{\circ}$ and $90^{\circ}$ incident angles. The initial kinetic energies of the hydrogen ion were ranged from 100 eV to 1,600 eV to study the layer-by-layer energy variation as a dependence of incident energies and angles. At low incident energies, the scattering energy transfer is dominated by the normal motion of surface layers due to thermal vibrations and multiple collision effects. For higher incident energies, the scattering energy transfer in a normal direction is greater than that in a parallel direction. In the case of penetration, the amount of transferred energies do not affect much on Ni layers at low incident energy. It was found channeling effects through Ni layers with increasing incident energies.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.272-273
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• 2001

We demonstrate the first separation of neutral molecules using optical forces. Unlike laser atomic cooling or optical tweezers, optical separation technique requires the manipulation of only one component of the molecular motion. Thus the mixtures can be separated, in principle, with less complex schemes. When an Intense nonresonant laser beam is focused onto a beam of molecules, the interaction between the laser electric field and the induced dipole moment of a molecule invokes a mechanical force on the molecule proportional to the field gradient and the molecular polarizability ($\alpha$) to mass (m) ratio $\alpha$/m. (omitted)

• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.574-578
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• 2013

In this work, the friction and diffusion coefficients of a tracer in a mesoscopic solvent are evaluated as a function of the tracer size by a hybrid molecular dynamics simulation where solute molecules evolve by Newton's equations of motion but the solvent evolves through the multi-particle collision dynamics. The friction coefficient is shown to scale linearly with the tracer size for larger tracers in accord with predictions of hydrodynamic theories. The diffusion coefficient of tracer is found to be inversely proportional to tracer size. The behavior of Stokes-Einstein formula is validated as a function of tracer size.

• Bulletin of the Korean Chemical Society
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• v.20 no.4
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• pp.445-450
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• 1999

Molecular dynamics (MD) simulation of non-rigid H-Y zeolite framework are performed at 298.15 and 5.0 K. Usual bond stretching, bond angle bending, torsional rotational, and non-bonded Lennard-Jones and electrostatic interactions are considered as intraframework interaction potentials. Calculated atomic parameters are in good agreement with the experiment, which indicates the successful reproduction of the framework structure and its motion. Both calculated bond lengths and bond angles are also in good agreement with the experiment except generally for a little longer bond lengths and a little smaller T-O-H bond angles. The calculated overall site occupation of HI keeps the order O(2) > O(3) > O(4) > O(t) at 298.15 K, which is very different from the experimental prediction, O(l) > O(3) > O(2) at 5 K. Calculated IR spectra of the H-Y zeolite framework show that most of the main peaks of the O-H bonds are in the broad region 3700-5000 cm-1 and that the O-T stretching bands appeared in 0-2000 cm-1 and at 2700 cm-1

• Bulletin of the Korean Chemical Society
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• v.21 no.3
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• pp.310-316
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• 2000

Molecular dynamics simulation studies for thermotropic liquid crystalline systems conposed of rodlike molecules with 6 Lennard-Jones interaction sites wre performed in NPT ensemble. Within the range of temperature studied, the system exhibited isotropic and smectic phase. For the characterization of the smectic phase, we examined the structure of the liquid crystalline phase via the radial distribution function, its longitudinal and transverse components to the director, and other orientational correlation function, its longitudinal and transverse components to the director, and other orientational correlation functions. In the smectic A phase, our results showed a large anisotropy in translational motion (i.e.,$D_⊥ >> D_∥$), and the decay of the collective orientational correlation function of rank two became slower than that of the single particle orientational correlation function of rank one. Comments on the spontaneous growth of orientational order directly from the isotropic phase are given.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.1
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• pp.60-67
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• 2005

Generally. in the molecular dynamics simulations. the Verlet neighboring list algorithm is used for the reduction of a simulation time On the other hand. the application of the Verlet neighboring list forces the time evolution of a simulation system to follow an unrealistic path in a phase space. In equilibrium state, it does not matter with the simulation results because the individual molecule's motion is originally random and any effect due to a small deviation from a real time evolution can be completely ignored. However, if an unsteady state is involved. such a deviation may significantly affect to the results. That is, there is a Possibility that the simulation results Provide ones with any misleading data In this study we evaluated the effect due to the Verlet neighboring list in performing the simulation of a non-equilibrium state and suggested the method to avoid it.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.73.2-73.2
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• 2010

In order to understand internal dynamics of starless cores, molecular line emissions are usually observed. From profiles of the molecular lines, internal motions of starless cores have been deduced using a simple radiative transfer model such as the two-layer model (Myers et al.1996). This brings complexities arising from the chemical evolution. The motivation of this study is to follow the chemical evolution of a starless core that goes through gravitational contraction. For this purpose, we have performed hydrodynamical simulations with a marginally unstable Bonnor-Ebert sphere as an initial condition. We follow the chemical evolution of this core with changing conditions such as the chemical reaction rate at the dust surface and the strength of radiation field that penetrate into the core. At the core center, the molecules suffer from a higher degree of molecular depletion on the dust covered by ice rather than on the bare silicate dust. The stronger radiation field dissociates more molecules at the core envelope. From analysis on the line profile using the two-layer model, we found that the speed of inward motion deduced from the HCN F = 2-1 line adequately traces the true infall speed, when the dust is covered by ice and the core is exposed to the diffuse interstellar radiation field. Under different conditions, the two-layer model significantly underestimate the infall speed.