• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.178-180
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• 2003

We performed semiempirical (AMl and ZINDO) and ab initio (HF and DFT) calculations, to investigate molecular structures and optical properties of DCM and its derivatives. DCM and its derivatives are used as a red fluorescent dopant of the organic electroluminescent host materials, $Alq_3$. We have studied the relationship between the molecular structure and the optical properties of these molecules for the improvement of EL efficiencies. Wavelength at the absorption maximum was found to be red-shifted when the molecule is substituted with both strong electron donating and withdrawing functional groups. A new red fluorescent dye was predicted by QSPR study based on calculations and experimental data.

• Bulletin of the Korean Chemical Society
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• v.25 no.5
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• pp.737-741
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• 2004

We presents new results for transport properties of dumbbell fluids by equilibrium molecular dynamics (EMD) simulations using Green-Kubo and Einstein formulas. It is evident that the interaction between dumbbell molecules is less attractive than that between spherical molecules which leads to higher diffusion and to lower friction. The calculated viscosity, however, is almost independent on the molecular elongation within statistical error bar, which is contradicted to the Stokes' law. The calculated thermal conductivity increases and then decreases as molecular elongation increases. These results of viscosity and thermal conductivity for dumbbell molecules by EMD simulations are inconsistent with the earlier results of those by non-equilibrium molecular dynamics (NEMD) simulations. The possible limitation of the Green-Kubo and Einstein formulas with regard to the calculations of viscosity and thermal conductivity for molecular fluids such as the missing rotational degree of freedom is pointed out.

• Korean Chemical Engineering Research
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• v.49 no.3
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• pp.361-366
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• 2011

By using Monte Carlo simulation method we developed a new molecular simulation software which can be used to predict the thermodynamic properties of organic compounds. Starting from molecular structure and intermolecular potential function, rigorous statistical mechanical principles give a probability distribution for the behavior of a system containing many molecules, which enables us to calculate macroscopic thermodynamic properties of the system. The software developed in this work, cheMC, is based on Windows platform providing with easy access. One can efficiently administrate simulations by using an intuitive interface equipped with visualization tool and chart generation. It is expected that molecular simulations supplement the equation of state approach and will play a more important role in the study of thermodynamic properties.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.4
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• pp.59-68
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• 1998

This study was to investigate the effect of chitosan molecular weight, its charge density, and its surface coating treatment on the antibacterial properties of paper. For this study, E.coil was used for antibacterial experiment. Results obtained were as follows : 1. The antibacterial properties of chitosan was significant on the surface-treated sheet. 2. Antibacterial property surface treatment was appeared to be effective when film was formed on the paper surface. 3. The antibacterial properties of chitosan-treated paper was dependent on the amount and the molecular weight of chitosan used. The lower the molecular weight of the chitosan down to 30,000 the better the antibacterial properties in this experiment. 4. Determination of the degree of chitosan-deacetylation by colloidal titration method was consistent with the more complicated and conventional FT-IR method.

• Parasites, Hosts and Diseases
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• v.37 no.4
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• pp.215-228
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• 1999

To choose one or more appropriate molecular markers or gene regions for resolving a particular systematic question among the organisms at a certain categorical level is still a very difficult process. The primary goal of this review, therefore, is to provide a theoretical information in choosing one or more molecular markers or gene regions by illustrating general properties and phylogenetic utilities of nuclear ribosomal DNA (rDNA) and mitochondrial DNA (mtDNA) that have been most commonly used for phylogenetic researches. The highly conserved molecular markers and/or gene regions are useful for investigating phylogenetic relationships at higher categorical levels (deep branches of evolutionary history). On the other hand, the hypervariable molecular markers and/or gene regions are useful for elucidating phylogenetic relationships at lower categorical levels (recently diverged branches). In summary, different selective forces have led to the evolution of various molecular markers or gene regions with varying degrees of sequence conservation. Thus, appropriate molecular markers or gene regions should be chosen with even greater caution to deduce true phylogenetic relationships over a broad taxonomic spectrum.

• Smart Structures and Systems
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• v.13 no.4
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• pp.685-709
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• 2014

Carbon nanotubes are due to their outstanding mechanical properties destined for a wide range of possible applications. Since the knowledge of the material behavior is vital regarding the possible applications, experimental and theoretical studies have been conducted to investigate the properties of this promising material. The aim of the present research is the calculation of mechanical properties and of the mechanical behavior of single wall carbon nanotubes (SWCNTs). The numerical simulation was performed on basis of a molecular mechanics approach. Within this approach two different issues were taken into account: (i) the nanotube geometry and (ii) the modeling of the covalent bond. The nanotube geometry is captured by two different approaches, the roll-up and the exact polyhedral model. The covalent bond is modeled by a structural molecular mechanics approach according to Li and Chou. After a short introduction in the applied modeling techniques, the results for the Young's modulus for several SWCNTs are presented and are discussed extensively. The obtained numerical results are compared to results available in literature and show an excellent agreement. Furthermore, deviations in the geometry stemming from the different models are given and the resulting differences in the numerical findings are shown. Within the investigation of the deformation mechanisms occurring in SWCNTs, the basic contributions of each individual covalent bond are considered. The presented results of this decomposition provide a deeper understanding of the governing deformation mechanisms in SWCNTs.

• Bulletin of the Korean Chemical Society
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• v.28 no.2
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• pp.200-206
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• 2007

Pharmacophore models for lymphocyte-specific protein tyrosine kinase (P56 LCK) were developed using CATALYST HypoGen with a training set comprising of 25 different P56 LCK inhibitors. The best quantitative pharmacophore hypothesis comprises of one hydrogen bond acceptor, one hydrogen bond donor, one hydrophobic aliphatic and one ring aromatic features with correlation coefficient of 0.941, root mean square deviation (RMSD) of 0.933 and cost difference (null cost-total cost) of 66.23. The pharmacophore model was validated by two methods and the validated model was further used to search databases for new compounds with good estimated LCK inhibitory activity. These compounds were evaluated for their binding properties at the active site by molecular docking studies using GOLD software. The compounds with good estimated activity and docking scores were evaluated for physiological properties based on Lipinski's rules. Finally 68 compounds satisfied all the properties required to be a successful inhibitor candidate.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.55.5-56
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• 2016

Turbulence plays an important role in molecular clouds. However, the properties of turbulence are poorly understood. In order to study the influence of turbulence in molecular clouds, we need to sample the turbulent properties in the full range of scales down to sonic scale. We mapped the $20^{\prime}{\times}60^{\prime}$ area covering the Orion Molecular Cloud (OMC) 1-4 region in HCN 1-0 and HCO+ 1-0 with Taeduk Radio Astronomy Observatory (TRAO) 14-m telescope as part of the TRAO key science program, "Mapping turbulent properties of star-forming molecular clouds down to the sonic scale (PI: Jeong-Eun Lee)". In addition, we combine our TRAO data with other molecular line maps ($^{13}CO$ 1-0, $C^{18}O$ 1-0, CS 1-0, $N_2H^+$ 1-0) obtained with the Nobeyama Radio Observatory (NRO) 45-m telescope. To analyze these data, we apply statistical methods, the principal component analysis (PCA) and spectral correlation function (SCF), which are known to be useful to study underlying turbulent properties and to quantitatively characterize cloud structure. We will present the preliminary results of observations and analyses.

• Macromolecular Research
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• v.9 no.1
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• pp.1-19
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• 2001

Poly(p-phenylene pyromellitimide) and poly(4,4'-biphenylene pyromellitimide) are representatives of fully rod-like polyimides. Their structure and properties in thin films are reviewed. The polymers exhibit some excellent properties such as high molecular packing coefficient, high mechanical modulus, and low thermal expansion coefficient, and low interfacial stress, so that they are very attractive to both industry and academia. However, these polymers are very brittle and thus practically useless. Some chemical modifications to improve such drawback with a little sacrifice of the high modulus are described: i) incorporation of short side groups into the polymer backbone and ii) insertion of proper linkages into the polymer backbone.

• International Journal of Precision Engineering and Manufacturing
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• v.5 no.4
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• pp.28-35
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• 2004

Stimulated by novel phenomena observed in molecular aggregates, recent developments in engineering fields of microscopic scales are creating tremendous opportunities for future nanotechnology-based applications. Investigation in the field involves sub-nanosecond or sub-micrometer interactions between extremely small systems, but researches, to date in these physical extremes have been quite limited. Here, we shed light on some of nanoscale phenomena using molecular dynamics simulation: visualization of various phenomena of nanoscales and exploration of size-dependent mechanical properties.