• Journal of Radiation Protection and Research
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• v.26 no.2
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• pp.93-99
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• 2001

Voxel head phantom for overcoming the limitation of mathematical phantom in depleting anatomical details was constructed and example dose calculation for BNCT was performed. The repeated structure algorithm of the general purpose Monte Carlo code, MCNP4B was applied for yokel Monte Carlo calculation. Simple binary yokel phantom and combinatorial geometry phantom composed of two materials were constructed for validating the voxel Monte Carlo calculation system. The tomographic images of VHP man provided by NLM(National Library of Medicine) were segmented and indexed to construct yokel head phantom. Comparison of doses for broad parallel gamma and neutron beams in AP and PA directions showed decrease of brain dose due to the attenuation of neutron in eye balls in case of yokel head phantom. The spherical tumor volume with diameter, 5cm was defined in the center of brain for BNCT dose calculation in which accurate 3 dimensional dose calculation is essential. As a result of BNCT dose calculation for downward neutron beam of 10keV and 40keV, the tumor dose is about doubled when boron concentration ratio between the tumor to the normal tissue is $30{\mu}g/g$ to $3{\mu}g/g$. This study established the voxel Monte Carlo calculation system and suggested the feasibility of precise dose calculation in therapeutic radiology.

• Bulletin of the Korean Chemical Society
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• v.25 no.6
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• pp.847-851
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• 2004

The complexation characteristics of tetramethyl (1) and tetraethyl esters (2) of p-tert-butylcalix[4]arene with alkali metal cations have been investigated by ab initio calculation. The structures of endo- or exocomplexation of the hosts in cone conformation with alkali metal ions have been optimized using HF/6-31G method followed by B3LYP/6-31G(d) single point calculation. B3LYP/6-31G(d) calculations suggest that exo-complexation efficiencies of sodium ion to the cavity of lower rim of hosts 1 and 2 are 27.1 and 25.8 kcal/mol better than that of potassium ion, respectively. The exo-complexation efficiencies of potassium ion to the cavity of lower rim of hosts 1 and 2 are 33.3 and 31.5 kcal/mol better than the endo-complexation inside the upper rim (four aromatic rings) as expected from the experimental results. B3LYP/6-31G(d) calculation of the ethyl ester 2 shows 29.5 and 30.8 kcal/mol better exo-complexation efficiency for both sodium and potassium ions than the methyl ester 1.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.10 no.1
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• pp.107-112
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• 2014

The Code of Federal Regulations, Title 10, Part 50, Appendix H requires surveillance program for reactor pressure vessel(RPV) that the peak neutron fluence at the end of the design life of the vessel will exceed $1.0E+17n/cm^2$ (E>1.0MeV). 2D/1D Synthesis method based on DORT 3.1 transport calculation code has been widely used to determine fast neutron(E>1.0MeV) fluence exposure to RPV in the beltline region. RAPTOR-M3G(RApid Parallel Transport Of Radiation-Multiple 3D Geometries) performing full 3D transport calculation was developed by Westinghouse and KRIST(Korea Reactor Integrity Surveillance Technology) and applied for the evaluations of In-Vessel and Ex-Vessel neutron dosimetry. The reaction rates from measurement and calculation were compared and the results show good agreements each other.

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3249-3252
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• 2013

We have explored the potential energy surface for the isomerization of the aniline (AN) radical cation to the 2-, 3-, and 4-methylpyridine (picoline, MP) radical cations using G3 model calculations. The isomerization may occur through the 1H-azepine (7-aza-cycloheptatriene) radical cation. A quantitative kinetic analysis has been performed using the Rice-Ramsperger-Kassel-Marcus theory, based on the potential energy surface. The result shows that isomerization between $AN^{+\bullet}$ and each $MP^{+\bullet}$ hardly occurs before their dissociations.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2301-2305
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• 2011

The potential energy surface (PES) for the loss of HCN or HNC from the pyrazine molecular ion was determined based on quantum chemical calculations using the G3//B3LYP method. Four possible dissociation pathways to form four $C_3H_3N^{+{{\bullet}}$ isomers were examined. A Rice-Ramsperger-Kassel-Marcus quasi-equilibrium theory model calculation was performed to predict the dissociation rate constant and the product branching ratio on the basis of the obtained PES. The resultant rate constant for the HCN loss agreed with the previous experimental result. The kinetic analysis predicted that the formation of $CH=CHN{\equiv}CH^{+{\bullet}}+HCN$ was predominant, which occurred by three consecutive steps, a C-C bond cleavage to form a linear intermediate, a rearrangement to form an H-bridged intermediate, and elimination of HCN.

• Bulletin of the Korean Chemical Society
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• v.10 no.4
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• pp.377-381
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• 1989

The spectroscopic properties of $FO^+$ and FO were investigated by ab initio calculation. Several different levels of theory, $MP3/6-31G^*,\;MP4/6-311G^*\;and\;CISD/6-31G^*$, were tried and compared with experimental results of FO. In the overall performance the CISD showed the best agreement. Based on these results the spectroscopic constants of $FO^+$ are predicted.

• Bulletin of the Korean Chemical Society
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• v.28 no.2
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• pp.235-240
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• 2007

Molecular structures were optimized for the 1,3-diethoxycalix[4]crown-5-ether (2) in the various isomers and their potassium-ion complexes by using B3LYP/6-31+G(d,p)//B1LYP/6-31G(d,p) method after ab initio RHF/6-31G calculation. The cone-shaped isomer of 2 with cr-binding mode has shown the strongest binding efficiency among the six different complexes attributed to seven electrostatic interactions between the potassium cation and the oxygen atoms of crown-5-ether and ethoxy groups of the host (2). The vibrational spectra of 2 and its K+-complexes were obtained by restricted Hartree-Fock (RHF) calculations with the 6-31G basis set. The characteristic vibrational frequencies of various C-O-C stretching and bending motions are analyzed.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.30-43
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• 2021

In the 2D/1D method, a global adjoint CMFD based on the generalized equivalence theory is built to synthesize the 2D radial MOC adjoint and 1D axial NEM adjoint calculation and also to accelerate the iteration convergence of 3D whole-core adjoint transport calculation. Even more important, an advanced yet accurate two-level (TL) CMFD acceleration technique is proposed, in which an equivalent one-group adjoint CMFD is established to accelerate the multi-group adjoint CMFD and then to accelerate the 3D whole-core adjoint transport calculation efficiently. Based on these method, a new code is developed to perform 3D adjoint neutron flux calculation. Then a set of VERA and C5G7 benchmark problems are chosen to verify the capability of the 3D adjoint calculations and the effectiveness of TL CMFD acceleration. The numerical results demonstrate that acceptable accuracy of 2D/1D adjoint calculations and superior acceleration of TL CMFD are achievable.

• Bulletin of the Korean Chemical Society
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• v.30 no.4
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• pp.837-845
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• 2009

We have performed DFT calculations to investigate the conformational characteristics and hydrogen bonds of the calix[6]arene (1) and p-tert-butylcalix[6]arene (2). The structures of various conformers of 1 were optimized by using the B3LYP/6-31G(d,p) and /6-31+G(d,p) methods followed by single point calculation of MPW1PW91/ 6-31G(d,p). The relative stability of the conformers of 1 is in the following order: cone (pinched: most stable) > partial-cone > cone (winged) $\sim$ 1,2-alternate $\sim$ 1,2,3-alternate > 1,4-alternate > 1,3-alternate > 1,3,5-alternate. The structures of different conformers of 2 were optimized by using the B3LYP/6-31G(d,p) method followed by single point calculation of MPW1PW91/6-31G(d,p). The relative stability of the conformers of 2 is in the following order: cone (pinched) > 1,2-alternate > cone (winged) > 1,4-alternate $\sim$ partial-cone > 1,2,3-alternate > 1,3,5alternate > 1,3-alternate. One of the important factors affecting the relative stabilities of the various conformers of the 1 and 2 is the number and strength of the intramolecular hydrogen bonds.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.3
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• pp.351-356
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• 2004

Selecting appropriate G values in flocculator operation is important to produce high quality filter effluent in water treatment plants. However, misunderstanding and misleading of G calculation for the case of having power sources more than one or many paddles with one power source in a flocculation basin sometimes have led to low performance in flocculation. Theoretical analysis confirmed that the total G value in one flocculation unit having power sources more than one or with many paddles is the root-square of the sum of square of individual G value. This analysis also can give a simple calculation method of G value for designers and operators in fields.