• Macromolecular Research
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• v.16 no.8
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• pp.686-694
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• 2008

We studied the molecular shapes and structural characteristics of a 33-armed, star polystyrene (PS-33A) and two $3^{rd}$-generation, dendrimer-like, star-branched poly(methyl methacrylate)s with different architectures (pMMA-G3a and PMMA-3Gb) and 32 end-branches under good solvent and theta ($\Theta$) solvent conditions by using synchrotron small angle X-ray scattering (SAXS). The SAXS analyses were used to determine the structural details of the star PS and dendrimer-like, star-branched PMMA polymers. PS-33A had a fuzzy-spherical shape, whereas PMMA-G3a and PMMA-G3b had fuzzy-ellipsoidal shapes of similar size, despite their different chemical architectures. The star PS polymer's arms were more extended than those of linear polystyrene. Furthermore, the branches of the dendrimer-like, star-branched polymers were more extended than those of the star PS polymer, despite having almost the same number of branches as PS-33A. The differences between the internal chain structures of these materials was attributed to their different chemical architectures.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.161-166
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• 2004

A study of argon droplet vaporization is conducted using molecular dynamics. Instead of using traditional method such as the Navier-Stokes equation. Molecular dynamics uses Lagrangian frame to describe molecular behavior in a system and uses only momentum and position data of all molecules in the system. So every property is not a hypothetical input but a statistical result calculated from the momentum and position data. This work performed a simulation of the first-order stability for phase transition of a three dementional submicron argon droplet within quiescent environment. Lennard-Jones 12-6 potential function is used as a intermolecular potential function. The molecular configuration is examined while an initially non-sperical droplet is changed into the spherical shape and droplet evaporates or condensates.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.121-126
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• 2003

A study of argon droplet vaporization is conducted using molecular dynamics, instead of using traditional methods such as the Navier-Stokes equation. Molecular dynamics uses Lagrangian frame to describe molecular behavior in a system and uses only momentum and position data of all molecules in the system. So every property is not a hypothetical input but a statistical result calculated from the momentum and position data. This work performed a simulation of the complete vaporization of a three dimensional submicron argon droplet within quiescent environment. Lennard-Jones 12-6 potential function is used as a intermolecular potential function. The molecular configuration is examined while an initially non-spherical droplet is changed into the spherical shape and droplet evaporates. And the droplet radius versus time is calculated with temperature and pressure profile.

• Transactions of the Society of Information Storage Systems
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• v.11 no.2
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• pp.36-40
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• 2015

The demand for flexible devices including solar cells, memories and batteries has increased rapidly over the past decades. In most flexible devices, polymer-based materials are used to enable the mechanical deformations such as bending or folding. Shape Memory Polymers (SMPs) is a high molecular compound polymer with flexibility and shape recovery characteristics. In this work, flexible shape memory device was fabricated by simply coating the conducting material, carbon nano-tube (CNT), on a shape memory polymer. Furthermore, durability of the device under various type of mechanical deformations was assessed. It is believed that the result of this work will aid in realization of a stretchable and wearable electronic device for practical applications.

• Publications of The Korean Astronomical Society
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• v.13 no.1 s.14
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• pp.149-166
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• 1998

The structure and environments of the molecular clouds near the SNR $HB3(G132.7\pm1.3)$ are studied. The molecular complex which is located at the southern rim of HB3 was proposed by former investigators as the one interacting with HB3. This complex region of $2^{\circ}\times2^{\circ}\;at\;l=133^{\circ}$ has been observed at $^{12}CO,\;^{13}CO,\;J=1-0\;at\;a\;1'$, resolution with the 14-m radio telescope at Taeduk Radio Astronomy Observatory. We have reached to the following four conclusions. The possibility that these molecular complex and HB3 are interacting with each other cannot be supported with any of our data. The morphologies of the two show no similarities. Neither particular features for the interaction are found in the CO lines. The hypothetical 'Molecular wall' which was expected to exist on the northwestern rim of HB3 as a cause for the noncircular morphology of HB3 is turned out to be nonexistent in CO. The molecular complex which resembles a 'bar' at a low resolution is now resolved into a U-shaped shell. It seems that the U-shape is consist of two independent components. No peculiarities, such as unseen masses or bright stars capable of forming HlI regions, are found within the U-shape region. The total mass included in the complex is estimated to be $M_{total}\;=\;2.9\~8.4\times10^5\;M_\bigodot$, which is in good agreement with previous observations within errors. Considering about 12 clumps distinguishable within the complex, the total mass implies that masses of each of clumps are on the order of $10^4\;M_\bigodot$, which makes these good objects for further studies in relation to star-formation. Especially the clumps associated with W3 are worthy for more high resolution observations for better understanding of astrophysical phenomenon ongoing in them.

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.38-38
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• 2003

The electrical properties of neurons are produced by the coordinated activity of ion channels (Hille, 1992). $K^{+}$ channels play a key role in shaping action potentials and in determining neural firing patterns. Small conductance $Ca^{2+}$-activated $K^{+}$ (S $K_{Ca}$ ) channels are involved in modulating the slow component of afterhyperpolarization (AHP) (Kohler et al., 1996). Here we examine whether rat type 2 S $K_{Ca}$ (rSK2) channels can affect the shape of the action potential and the neural firing pattern, by overexpressing rat SK2 channels in Aplysia neuron R15. Our results show that rSK2 overexpression decreased the intraburst frequency and changed the regular bursting activity of neurons to an irregular bursting or beating pattern in R15, Furthermore, the overexpression of rSK2 channels increased AHP and reduced the duration of the action potential. Thus, our results suggest that ectopic S $K_{Ca}$ channels play an important role in regulating the filing pattern and the shape of the action potential.ntial.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.337-342
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• 2007

In this study, molecular dynamics simulation of nano imprint lithography in which patterned stamp is pressed onto amorphous polyethylene(PE) surface are performed to study the behaviour of polymer. Force fields including bond, angle, torsion, and Lennard Jones potential are used to describe the inter-molecular and intra-molecular force of PE molecules and stamp, substrate. Periodic boundary condition is used in horizontal direction and canonical NVT ensemble is used to control the system temperature. As the simulation results, the behaviour of polymer is investigated during the imprinting process. The mechanism of polymer deformation is studied by means of inspecting the surface shape, volume, density, atom distribution. Deformation of the polymer resist was found for various of the stamp geometry and the alignment state of the polymer molecules.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.1112-1117
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• 2003

Polarized Fourier transform infrared (IR) absorption is used to probe molecular conformation in a ferroelectric liquid crystal (FLC) during the reorientation induced by the external field. Spectra of planar aligned cells of FLC W314 are measured as functions of IR polarizer orientation and electric field applied to the FLC. The time evolution of the dichroism of the absorbance due to biphenyl core and alkyl tail molecular vibration modes, is observed. Static IR dichroism experiments show a W314 dichroism structure in which the principal axis of dielectric tensor from molecular core vibration are tilted further from the smectic layer normal than those of the tail. This structure indicates the effective binding site in which the molecules are confined in the Sm-C phase has, on average, "zig-zag" shape and this zig-zag binding site structure is rigidly maintained while the molecular axis rotates about the layer normal during field-induced switching.

• Interaction and multiscale mechanics
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• v.6 no.3
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• pp.301-316
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• 2013

The influence of indenter geometry on nanoindentation was studied using a static molecular dynamics simulation. Dislocation nucleation, dislocation locks, and dislocation movements during nanoindentation into Al (001) were studied. Spherical, rectangular, and Berkovich indenters were modeled to study the material behaviors and dislocation activities induced by their different shapes. We found that the elastic responses for the three cases agreed well with those predicted from elastic contact theory. Complicated stress fields were generated by the rectangular and Berkovich indenters, leading to a few uncommon nucleation and dislocation processes. The calculated mean critical resolved shear stresses for the Berkovich and rectangular indenters were lower than the theoretical strength. In the Berkovich indenter case, an amorphous region was observed directly below the indenter tip. In the rectangular indenter case, we observed that some dislocation loops nucleated on the plane. Furthermore, a prismatic loop originating from inside the material glided upward to create a mesa on the indenting surface. We observed an unusual softening phenomenon in the rectangular indenter case and proposed that heterogeneously nucleating dislocations are responsible for this.

• Applied Microscopy
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• v.25 no.1
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• pp.15-29
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• 1995

Legumin was purified from the endosperm cells of the ginseng seed and analyzed its characteristics. Distributional patterns of the legumin in the endosperm cells were identified using the immunocytochemical method. Legumin was glycoprotein composed of two subunits, molecular weights about 33,000 and 25,000 respectively. The molecular shape of purified legumin stained negatively seems to have hexagonal structure about 10 nm in size. It was localized at the rER, dictyosomes, and in the vacuoles at the early developing stage. Legumin was glycosylated in the dictyosomes and transported from the dictyosomes to the vacuoles. Legumin was accumulated into the central vacuole via the dictyosomes while the endosperm cells were developing. The armorphous proteins containing legumin were scattered randomly within the central vacuoles, which were aggregated together and became gradually spherical shape. Legumin was distributed within the globular protein bodies in the endosperm cells of matured seed. However legumin was not found in the globoids located in the protein bodies.