• Bulletin of the Korean Chemical Society
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• v.32 no.11
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• pp.3851-3852
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• 2011

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.301-301
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• 2006

The physical properties of well-defined star-shape polystyrenes with high number of arms (6 to 57 arms) in good and theta solvents were studied using synchrotron X-ray scattering. The scattering profiles for multi-armed polystyrenes shown the molecular shape is changed according to increasing of number of arm. From various parameters which were obtained from scattering profiles, the molecular shape was determined more detail. As results, the molecular shape was changed from a fuzzy-ellipsoid for 6-armed PS to a fuzzy-sphere sphere for 57-armed PS according to increasing of number of arm.

• Journal of Photoscience
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• v.3 no.3
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• pp.147-151
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• 1996

Dynamics of contact ion-pair between 1, 2, 4, 5-tetracyanobenzene anion and cation of biphenyl derivatives was investigated on the picosecond time scale. Solvent effect on the electron transfer was observed and electron transfer rates were examined using Marcus equation which contains distance dependence of the electron transfer rate in the frequency factor, along with the consideration of molecular shape. From the discussion based on disk model for molecular shape, contribution of interring torsional motion of biphenyl to the inner-sphere reorganization energy is strongly suggested, which leads to the physical explanation for the observed solvent effect on the rate of electron transfer.

• Korean Journal of Computational Design and Engineering
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• v.14 no.6
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• pp.404-414
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• 2009

In the computational molecular analysis, 3D structural comparison for protein searching plays a very important role. As protein databases have been grown rapidly in size, exhaustive search methods cannot provide satisfactory performance. Because exhaustive search methods try to handle the structure of protein by using sphere set which is converted from atoms set, the similarity calculation about two sphere sets is very expensive. Instead, the filter-and-refine paradigm offers an efficient alternative to database search without compromising the accuracy of the answers. In recent, a very fast algorithm based on the inter-atomic distance has been suggested by Ballester and Richard. Since they adopted the moments of distribution with inter-atomic distance between atoms which are rotational invariant, they can eliminate the structure alignment and orientation fix process and perform the searching faster than previous methods. In this paper, we propose a new 3D shape descriptor. It has properties of the general shape distribution and useful property in screening the molecular database. We show some experimental results for the validity of our method.

• Textile Coloration and Finishing
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• v.27 no.4
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• pp.270-274
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• 2015

Molecules always show broad absorption band envelopes, and this results from the vibrational properties of bonds. The width of an absorption band can have an important influence on the color of a dye. A narrow band imparts a bright, spectrally pure color to the dye, whereas a broad band can give the same hue, but with a much duller appearance. Typically, half-band widths of cyanine dyes are about 25nm compared to value of over 50nm for typical merocyanine dyes. Thus, cyanine dyes are exceptionally bright. The factors influencing the width of an absorption band can be understood with reference to the Morse curves. The width of the absorption band depends on how closely the bond order of the molecules in the first excited state resembles that in the ground state. We have quantitatively evaluated the "molecular structure-absorption band shape" relationship of dye molecules by means of Pariser-Parr-Pople Molecular Orbital Method(PPP-MO).

• Journal of radiological science and technology
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• v.1 no.1
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• pp.55-59
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• 1978

The photographic characteristics have been studied in relation with various molecular weights of Polyvinylpyrrolidone(PVP). The shape of silver halogen crystals by physical ripening of mixture of photographic gelatine and various molecular weights of PVP were observed. Then, the photographic characteristics have been studied by chemical ripening. Results were concluded as follows: 1. All of the crystals have formed in the shape of (100) or (111). 2. Photographic characteristics were inferior by using PVP of higher molecular weight. 3. Photographic characteristics were superior by using PVP of lower molecular weight. 4. Photographic characteristic were compared with various Emulsion thickness and Tested Resolving power.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.1-2
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• 2006

Polymer architecture plays a great role in determining the properties of functional polymers. This lecture will explore the design and the synthesis of polymers with controlled architecture and functionality. Especially featured will be star and dendritic architectures where the functional group placement and the molecular shape can be controlled. This will be followed by examples of applications illustrated with a few model systems of functional polymers designed for use in areas such as organic electronics, catalysis, surface patterning, separation and molecular recognition, and polymer therapeutics.

• Coupled systems mechanics
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• v.6 no.1
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• pp.41-54
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• 2017

Shape-memory alloys (SMA) have interesting behaviors and important mechanical properties due to the solid-solid phase transformation. These phenomena are dominated by the evolution of microstructures. In recent years, the microstructures in SMAs have been studied extensively and modeled using molecular dynamics (MD) simulations. However, it remains difficult to identify the crystal variants in the simulation results, which consist of large numbers of atoms. In the present work, a method is developed to identify the austenite phase and the monoclinic martensite crystal variants in MD results. The transformation matrix of each lattice is calculated to determine the corresponding crystal variant. Evolution of the volume fraction of the crystal variants and the microstructure in Ni-Ti SMAs under thermal and mechanical boundary conditions are examined. The method is validated by comparing MD-simulated interface normals with theoretical solutions. In addition, the results show that, in certain cases, the interatomic potential used in the current study leads to inconsistent monoclinic lattices compared with crystallographic theory. Thus, a specific modification is applied and the applicability of the potential is discussed.

• Polymer(Korea)
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• v.24 no.3
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• pp.333-341
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• 2000

Blends consisting of linear shape polylactic acid and star shape polylactic acid (L-PLLA/S-PLLA) have been prepared by melt and solution blending. The effect of blending method on the thermal properties and crystallization behavior of L-PLLA/S-PLLA blends has been investigated. The molecular weight decrease was revealed both in melt and solution blending. S-PLLA was found to be more stable than L-PLLA in the reduction of molecular weight during the course of blending due to its star shape structure. As a result, broad molecular weight distribution was obtained in solution blending. It was found that melting temperature and glass transition temperature decrease with increasing S-PLLA content. Blending method had large influence on the glass transition temperature of PLLA blends, while less effect on melting temperature. From DSC results, it can be noticed that solution blending is more effective blending method to obtain higher crystallinity than melt blending for S-PLLA and blend with higher S-PLLA content.

• Bulletin of the Korean Chemical Society
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• v.28 no.10
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• pp.1697-1704
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• 2007

We present results for transport properties of diatomic fluids by isothermal-isobaric (NpT) equilibrium molecular dynamics (EMD) simulations using Green-Kubo and Einstein formulas. As the molecular elongation of diatomic molecules increases from the spherical monatomic molecule, the diffusion coefficient increases, indicating that longish shape molecules diffuse more than spherical molecules, and the rotational diffusion coefficients are almost the same in the statistical error since random rotation decreases. The calculated translational viscosity decreases with the molecular elongation of diatomic molecule within statistical error bar, while the rotational viscosity increases. The total thermal conductivity decreases as the molecular elongation increases. This result of thermal conductivity for diatomic molecules by EMD simulations is again inconsistent with the earlier results of those by non-equilibrium molecular dynamics (NEMD) simulations even though the missing terms related to rotational degree of freedom into the Green-Kubo and Einstein formulas with regard to the calculation of thermal conductivity for molecular fluids are included.