• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.10A
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• pp.906-911
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• 2005

In this paper, for spatial multiplexing with limited feedback, we propose subspace method based preceding in which the active bases are selected at the receiver from a finite number of basis sets Down at both receiving and transmitting ends, conveyed to the transmitter using limited feedback, and assembled into a preceding matrix at the transmitter. The selected bases are conveyed to the transmitter using feedback information on both the index of the selected basis set, which defines the most appropriate set of coordinates for describing a multiple-input multiple-output (MIMO) channel, and the principal bases maximizing the capacity in the selected basis set. We show that the proposed subspace method based preceding provides a capacity similar to that of the closed-loop MIMO even with limited feedback.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.6
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• pp.1161-1166
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• 2005

In this paper, for spatial multiplexing with limited feedback, we propose subspace based precoding in which the active bases are selected at the receiver from a finite number of basis sets known at both receiving and transmitting ends, conveyed to the transmitter using limited feedback, and assembled into a preceding matrix at the transmitter. The selected bases are conveyed to the transmitter using feedback information on both the index of a basis set, which indicates the most appropriate set of coordinates for describing a MIMO channel, and the active bases having the significant amounts of energy in the selected basis set. We show that the proposed subspace based precoding provides capacity similar to that of the closed-loop MIMO even with limited feedback.

• Journal of the Korean Chemical Society
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• v.37 no.4
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• pp.408-415
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• 1993

Systematic ab initio SCF calculations have been performed on the hydrogen-bonded dimers of fluoromethanes involving $CH_4,\;CH_3F,\;CH_2F_2\;and\;CHF_3$ with ammonia and water applying basis sets of 9s5p/5s and 9s5p1d/5p1d. Various ground state properties of these stable dimeric complexes have been evaluated. We compared these with corresponding properties of isolated monomers. We report equilibrium geometries, stabilization energies, dipole moments and force constants of intermolecular bonds. The effects arising as a consequence of the non-additive behavior of hydrogen bonding in chain-like oligomers are discussed. Systematic, methodical errors due to the use of the SCF approximation and the basis set dependence of the computed results are pointed out.

• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1397-1402
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• 2014

The complete active space self-consist field method followed by the internally contracted multireference configuration interaction method has been used to compute the potential energy curves of $X^2\prod_g$, $a^4\prod_u$, $A^2\prod_u$, $b^4\sum_{g}^{-}$, and $B^2\sum_{g}^{-}$ states of $S{_2}^+$ cation with large correlation-consistent basis sets. Utilizing the potential energy curves computed with different basis sets, the spectroscopic parameters of these states were evaluated. Finally, the transition dipole moment and the Franck-Condon factors of the transition from $A^2\prod_u$ to $X^2\prod_g$ were evaluated. The radiative lifetime of $A^2\prod_u$ is calculated to be 887 ns, which is in good agreement with experimental value of $805{\pm}10$ ns.

• Bulletin of the Korean Chemical Society
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• v.26 no.1
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• pp.119-126
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• 2005

The geometrical parameters, vibrational frequencies, and relative energies of H$_2$(A$_{n+1}$X$_{2n}$)H$_2$ (A=C or Si, X=O or S, n = 1-2) oligomers have been investigated using high level ab initio quantum mechanical techniques with large basis sets. The equilibrium geometries have been optimized at the self-consistent field (SCF), the coupled cluster with single and double excitation (CCSD), and the CCSD with connected triple excitations [CCSD(T)] levels of theory. The highest level of theory employed in this study is cc-pVTZ CCSD(T). Harmonic vibrational frequencies and IR intensities are also determined at the SCF level of theory with various basis sets and confirm that all the optimized geometries are true minima. Also zero-point vibrational energies have been considered to predict the dimerization and the relative energies.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.87-98
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• 2024

This study was conducted to investigate the efficiency of the filtering sets composed of fiberboards, which were fabricated with lignocellulosic fiber and cork oak bark-based activated carbon (COA), as well as traditional Korean paper handmade from mulberry trees (KP) for the filtration of PM, TVOC and HCHO. Three-layers fiberboards (WRF) were fabricated with wood fiber in its surface layers and recycled fiber/COA in its core layer using a protein-based adhesive with the resin content of 8%. Filtering sets were composed of three WRF and one sheet of KP. Concentrations of PM, TVOC and HCHO generated with the combustion of a incense in a sealed laboratory hood were reduced efficiently with the operation of air-purifier installed the filtering sets. Except for the WRF fabricated with 4%/4% resin contents, other WRF were prepared with 5%/3% and 6%/2% resin contents in surface/core layers, and then the WRF were used with KP for the fabrication of filtering sets. Filtration efficiency of the filtering sets was improved as the core-layer resin content applied in the fabrication of WRF decreased. In addition, filtration efficiency of the WRF-based filtering set fabricated with KP of 25 g/m² basis weight was higher than that with KP of 45 g/m² basis weight. Filtering sets composed of three-layers fiberboards (RWF) that recycled fiber and wood fiber/COA were used in its surface and core layers, respectively, and KP-25g showed higher filtration efficiency than those of WRF-based filtering sets. Air-inhalation equipment installed the RWF-based, WRF-based filtering sets and without filtering set were operated in small indoor and large outdoor spaces. Efficiency for filtering PM and TVOC of the RWF-based filtering sets was higher than that of other filtering sets. It is concluded that fiberboard-based filtering sets composed of RWF and KP-25g can be used as a filter for reducing the concentrations of PM and TVOC existed in indoor and outdoor spaces.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.4
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• pp.403-415
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• 1999

To properly assess air pollution levels, application of quality assurance and quality control(QA/QC) is believed to be an essential step. In order to cope with such scientific principle, a field study was designed with an aim of comparing: 1) the methods of calibration for airborne pollutants and 2) the protocols developed for their measurements. Measurements were made at Han Yang University, Seoul during 29 May through 1 June 1998 under the management of the Division of Measurements and Analysis(DMA) of Korean Society for Atmospheric Environment(KOSAE). In this work, we report our results of intercomparative measurements on several gaseous criteria pollutants that were investigated mainly by the two institutes-Seoul National University(SNU) and the Korean Research Institute for Standards and Science(KRISS). Although measurements of major gaseous pollutants had been made routinely by many scientific institutes and organizations in Korea, most scientists involved in those studieswere obliged to do their experiments on the basis of their own procedural steps spaning from the preparation of gaseous standards to the methodological selections for the calibration. Hence, this campaign offered a unique opportunity to examine many important aspects on the measurements of these important gaseous pollutants. In the course of our study, we investigated the compatibility of data sets obtained by the two institutes in concert with reference data sets collected concurrently from a government-managed monitoring station. On the basis of our study, we conclude that different data sets made by different participants during this campaign agree well within the reasonable range of uncertainties.low, which indicated that during this period the potential acidity of precipitation was high but the neutralizing capacity was low. For Spring, pAi was very low but pH was slightly high. This was likely due to the large amount of $CaCO_3$ in the soil particles transported over a long range from the Chinese continent that were incorporated into the precipitation, and then neutralized the acidifying species with its high concentraton.

• Bulletin of the Korean Chemical Society
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• v.23 no.9
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• pp.1267-1271
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• 2002

The conformation dependences of basis set superposition errors (BSSE) for 1,2-difluoroethane (DFE) and 1,2-dimethoxyethane (DME) molecules have been estimated using counterpoise method at the Moller-Plesset second order perturbation (MP2) level of theory with various basis sets, assuming that all BSSE dependences on conformations are due to the change in CC bond. The BSSE on the energy differences between eclipsed and gauche forms of DFE are in the range of 0.2-1.2 kcal/mol and those between local minima, gauche and anti forms, are less than 0.2 kcal/mol. For the larger DME molecule, the BSSE differences between local minima are still less than 0.4 kcal/mol, but may not be ignored compared to the energy differences of 0.2-3.0 kcal/mol between conformers.

• Bulletin of the Korean Chemical Society
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• v.15 no.11
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• pp.996-1000
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• 1994

Ab initio calculations with various basis sets have been carried out to investigate the geometries and ring inversion barrier of $R_2TiC_3H_6\;and\;R_2TiS_3$, R=Cp and Cl. Optimized geometries of $R_2TiC_3H_6$ showed the four membered ring was planar on Cs symmetry. However, $R_2TiS_3$ complexes were optimized to be stable in the puckered form. The smallest Basis III with STO-3G on Cp ligands gave reasonable results for the calculations of metallocene. The energy barrier for the ring inversion of metallacyclosulfanes, $Cp_2TiS_3$ was computed to be 8.72 kcal/mol at MP2 level. For the Cl system, we reproduced the molecular structure and ring inversion energy with Basis V.

• Journal of the Korean Chemical Society
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• v.47 no.4
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• pp.325-333
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• 2003

The geometrical parameters, vibrational frequencies, and relative energies for 1,2-, 1,3-dioxetanes, and 1,3-cyclodisiloxane have been investigated using high level ab initio quantum mechanical techniques with large basis sets. The geometries have been optimized at the self-consistent field(SCF), the single and double excitation configuration interaction(CISD), the coupled cluster with single and double excitation(CCSD), and the CCSD with connected triple excitations[CCSD(T)] levels of theory. The highest level of theory employed in this study is TZ2P CCSD(T). Harmonic vibrational frequencies and IR intensities are also determined at the SCF level of theory with various basis sets and confirm that all the optimized geometries are true minima. Also zero-point vibrational energies have been considered to predict the dimerization energies for 1,2- and 1,3-isomers.