• Journal of the Korean Chemical Society
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• v.54 no.4
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• pp.387-394
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• 2010

The theoretical calculations for $B_nH_n$, $B_nH_{n+1}$, $B_nH_{n+2}$ (n = 3-6) have been considered at the B3LYP level of theory with the 6-311G$^*$ basis set. The optimized geometries, harmonic vibrational frequencies, and binding energies are evaluated to elucidate the thermodynamic stability and spectroscopic properties. The harmonic vibrational frequencies for the molecules considered in this study show all real numbers implying true minima and the binding energies are corrected using zero-point vibrational energies (ZPVE). The binding energies and average energies due to increasing of BH monomer are predicted.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.2
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• pp.197-208
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• 2000

Choi et al./sup 1)/ presented the total Lagrangian formulation based upon the degenerated shell element. Geometrically correct formulation is developed by updating the direction of normal vectors and taking into account the second order rotation terms in the incremental displacement field. Assumed strain concept is adopted in order to overcome the shear locking phenomena and to eliminate the spurious zero energy mode. In this paper, for the ultimate strength analysis of stiffened shell structures considering effects of residual stresses, the return mapping algorithm based on the consistent elasto-plastic tangent modulus is applied to anisotropic shell structures. In addition, the load/displacement incremental scheme is adopted for non-linear F.E. analysis. Based on such methodology, the computer program is developed and numerical examples to demonstrate the accuracy and the effectiveness of the proposed shell element are presented and compared with the results in literatures.

• Nuclear Engineering and Technology
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• v.21 no.3
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• pp.171-185
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• 1989

On the basis of equal health hazard risk, economic assessment of nuclear was compared with that of coal for the expansion planning of electric power generation in the year 2000. In comparing health risks, the risk of coal was roughly ten times higher than that of nuclear according to various previous risk assessments of energy system. The zero risk condition can never be achievable. Therefore, only excess relative health risk of coal over nuclear was considered as social cost. The social cost of health risk was estimated by calculation of mortality and morbidity costs. Mortality cost was ＄250,000 and morbidity cost was ＄90,000 in the year 2000.(1986US＄) Through Cost/Benefit Analysis, the optimal emission standards of coal-fired power generation were predicted. These were obtained at the point of least social cost for power generation. In the year 2000, the optimal emission standard of SOx was analyzed as 165ppm for coal-fired power plants in Korea. From this assessment, economic comparison of nuclear and coal in the year 2000 showed that nuclear would be more economical than coal, whereas uncertainty of future power generation cost of nuclear would be larger than that of coal.

• Nuclear Engineering and Technology
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• v.3 no.1
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• pp.3-7
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• 1971

A method for determining dead times of a G.M. detector as a function of the count rate has been investigated using the Mn$^{56}$ radioactive sample. The formula, (equation omitted), seems to be useful for determining a relation between the dead time and the count rate. Here (equation omitted)(N$_1$) is the dead time for the count rate N$_1$, N$_1$is the count rate at time zero, Nt is the count rate at time t, λ is the radioactive decay constant of the sample used, and t is the time between the first and second runs. When all the counting data were corrected for the dead times evaluated with this formula and then a variation of these corrected counting data with rime was observed, the results showed quite a good agreement with the published data for the radioactive decay of Mn$^{56}$ . Besides, it appears that the dead time decreases as the count rate increases in a dead time-to-count rate relation obtained by the same formula.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.201-207
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• 2004

Dissolved air flotation (DAF) is a solid-liquid separation process that uses fine rising bubbles to remove particles in water. Most of particle-bubble collision occurs in the DAF contact zone. This initial contact considered by the researchers to play a important role for DAF performance. It is hard to make up conceptual model through simple mass balance for estimating collision efficiency in the contact zone because coupled behavior of the solid-liquid-gas phase in DAF system is 90 complicate. In this study, 2-phase(gas-liquid) flow equations for the conservation of mass, momentum and turbulence quantities were solved using an Eulerian-Eulerian approach based on the assumption that very small particle is applied in the DAF system. For the modeling of turbulent 2-phase flow in the reactor, the standard $k-{\varepsilon}$ mode I(liquid phase) and zero-equation(gas phase) were used in CFD code because it is widely accepted and the coefficients for the model are well established. Particle-bubble collision efficiency was calculated using predicted turbulent energy dissipation rate and gas volume fraction. As the result of this study, the authors concluded that bubble size and recycle ratio play important role for flow pattern change in the reactor. Predicted collision efficiency using CFD showed good agreement with measured removal efficiency in the contact zone. Also, simulation results indicated that collision efficiency at 15% recycle ratio is higher than that of 10% and showed increasing tendency of the collision efficiency according to the decrease of the bubble size.

• Journal of the Korean Chemical Society
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• v.21 no.2
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• pp.75-82
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• 1977

The isotope effect of pure liquid on vapor pressure is examined, and the vapor pressure ratios of two different isotopes are calculated. Based on the Significant Structure Theory of Liquids, the effect of molecular weight and the effect of moments of inertia are dominant in ordinary/trans-$d_2$ ethylene isotopes; the effect of hindered rotational zero-point energy is dominant in trans-$d_2$/cis-$d_2$ ethylene isotopes; and the effect of intermolecular potential difference is found in $CH_3OH/CH_3OD$ isotopes. In the isotopes of $CH_4/CD_4,\;SiH_4/SiD_4\;and\;GeH_4/GeD_4$, the weight effect decrease in the order of $CH_4/CD_4 >SiH_4/SiD_4 >GeH_4/GeD_4$.

• Journal of Environmental Policy
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• v.8 no.3
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• pp.181-206
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• 2009

The purpose of this paper is to analyze economic adequacy by estimating the benefit-cost for bird eco-park, eco-center, eco-river, and eco-waterway, which will be built in the new town of Kimpoo, Yangchon. This paper attempts an economic analysis for the development of an eco-friendly new town. The rates of B/C (benefit-cost) in all scenarios are over one. Especially, the B/C rate of the eco-center is the most efficient of the four eco-facilities by 5.02 - 3.75. In addition, the construction costs of the five eco-facilities are assumed to be 50 percent higher, though their economic soundness is maintained. This paper implies that providing ecological variety is one of the core components in constructing housing complexes and suggests that the construction of housing be harmonized with zero-carbon and energy efficient methods.

• Journal of Radiation Protection and Research
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• v.41 no.4
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• pp.378-383
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• 2016

Background: Radiation dose rates in PRIDE facility is evaluated quantitatively for assessing radiation safety of workers because of large amounts of depleted uranium being handled in PRIDE facility. Even if direct radiation from depleted uranium is very low and will not expose a worker to significant amounts of external radiation. Materials and Methods: ORIGEN-ARP code was used for calculating the neutron and gamma source term being generated from depleted uranium (DU), and the MCNP5 code was used for calculating the neutron and gamma fluxes and dose rates. Results and Discussion: The neutron and gamma fluxes and dose rates due to DU on spherical surface of 30 cm radius were calculated with the variation of DU mass and density. In this calculation, an imaginary case in which DU density is zero was added to check the self-shielding effect of DU. In this case, the DU sphere was modeled as a point. In case of DU mixed with molten salt of 50-250 g, the neutron and gamma fluxes were calculated respectively. It was found that the molten salt contents in DU had little effect on the neutron and the gamma fluxes. The neutron and the gamma fluxes, under the respective conditions of 1 and 5 kg mass of DU, and 5 and $19.1g{\cdot}cm^{-3}$ density of DU, were calculated with the molten salt (LiCl+KCl) of 50 g fixed, and compared with the source term. As the results, similar tendency was found in neutron and gamma fluxes with the variation of DU mass and density when compared with source spectra, except their magnitudes. Conclusion: In the case of the DU mass over 5 kg, the dose rate was shown to be higher than the environmental dose rate. From these results, it is concluded that if a worker would do an experiment with DU having over 5 kg of mass, the worker should be careful in order not to be exposed to the radiation.

• Journal of The Korean Astronomical Society
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• v.48 no.6
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• pp.343-355
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• 2015

There is much observational evidence that active star formation is taking place in the Hii regions Sh 2-255 – 257. We present a photometric study of this star forming region (SFR) using imaging data obtained in passbands from the optical to the mid-infrared, in order to study the star formation process. A total of 218 members were identified using various selection criteria based on their observational properties. The SFR is reddened by at least E(B −V ) = 0.8 mag, and the reddening law toward the region is normal (R_V = 3.1). From the zero-age main sequence fitting method it is confirmed that the SFR is 2.1 ± 0.3 kpc from the Sun. The median age of the identified members is estimated to be about 1.3 Myr from a comparison of the Hertzsprung-Russell diagram (HRD) with stellar evolutionary models. The initial mass function (IMF) is derived from the HRD and the near-infrared (J, J −H) color-magnitude diagram. The slope of the IMF is about Γ = −1.6 ± 0.1, which is slightly steeper than that of the Salpeter/Kroupa IMF. It implies that low-mass star formation is dominant in the SFR. The sum of the masses of all the identified members provides the lower limit of the cluster mass (169M_⊙). We also analyzed the spectral energy distribution (SED) of pre-main sequence stars using the SED fitting tool of Robitaille et al., and confirm that there is a significant discrepancy between stellar mass and age obtained from two different methods based on the SED fitting tool and the HRD.

• Earthquakes and Structures
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• v.13 no.5
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• pp.429-442
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• 2017

Dry bridges have been widely applied in the Qinghai-Tibet Railway (QTR) to minimize the thermal disturbance of engineering to the permafrost. However, because the Qinghai-Tibet Plateau is an area with a high potential occurrence of earthquakes, seismic action can easily destroy the dry bridges. Therefore, a three-dimensional numerical model, with consideration of the soil-pile interactions, is established to investigate the thermal characteristics and their impact on the seismic response of the dry bridge in permafrost region along the QTR. The numerical results indicate that there exist significant differences in the lateral displacement, shear force, and bending moment of the piles in different thermal conditions under seismic action. When the active layer become from unfrozen to frozen state, the maximum displacement of the bridge pile reduces, and the locations of the zero and peak values of the shear force and bending moment also change. It is found that although the higher stiffness of frozen soil confines the lateral displacement of the pile, compared with unfrozen soil, it has an adverse effect on the earthquake energy dissipation capacity.