• Journal of Advanced Marine Engineering and Technology
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• v.29 no.4
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• pp.391-398
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• 2005

In this investigation, turbulent premixed combustion and flame front propagation in a gas turbine combustion chamber is studied. Direct numerical simulation of turbulent reacting flows demands extremely high computational resources, especially in more complicated geometry. The alternative choice may be left for Large Eddy Simulation (LES) by which only large scales are solved directly. In combustion problems, capturing the large scales' behavior without solving the details of small scales is a difficult task. Using a transport equation for description of the flame front propagation and therefore avoiding the calculation of inner flame structure is the basic idea of this study. For this purpose. the so-called G-equation has been used by which any iso-level of the G variable provides the flame location. A comparison with the experiment indicates that the present method can predict a turbulent velocity field and also capture a instantaneous 3-dimensional flame structure.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.8
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• pp.1127-1136
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• 2013

Four rumen-fistulated crossbred beef cattle (Brahman native) were randomly assigned according to a $4{\times}4$ Latin square design experiment to be fed plant herb supplements in their concentrate mixture. The treatments were: without herb supplementation (Control), lemongrass meal supplementation at 100 g/d (L), lemongrass meal supplementation at 100 g/d plus peppermint powder at 10 g/d (LP), and lemongrass meal supplementation at 100 g/d plus peppermint powder at 10 g/d with garlic powder 40 g/d (LPG), respectively. Based on the present study, the DMI and apparent digestibility of DM, OM, aNDF and ADF were not affected by dietary herb supplementation while CP digestibility tended to be decreased by herb supplement. Moreover, $NH_3$-N and BUN were decreased in all herb supplemented treatments and there was a tendency to an increase in ruminal pH in all herb supplemented groups. While there was no change in TVFA and C4 among lemongrass treatments, C2 was decreased in all herb supplemented treatments while C3 was increased. Methane production by calculation was the lowest in the LP and LPG groups. Population sizes of bacteria and protozoa were decreased in all herb supplemented groups, but not fungal zoospores. In all supplemented groups, total viable and proteolytic bacteria were decreased, while amylolytic and cellulolytic bacteria were similar. More importantly, in all herb supplemented groups, there were higher N balances, while there was no difference among treatments on purine derivative (PD) excretion or microbial N. Based on the results above, it could be concluded that there was no negative effect on ruminal fermentation characteristics and nutrient utilization by plant herb supplement, but protozoal population and $CH_4$ production were reduced. Thus, lemongrass alone or in combination with peppermint and garlic powder could be used as feed additives to improve rumen fermentation efficiency.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.25 no.1
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• pp.72-76
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• 1980

The present studies were carried out to develope a simple quantitative analysis for saponins in ginseng by hemolysis. Erythrocytes from pig, rabbit, human and cattle were useful for this purpose. Erythrocytes could be stored at $4^{\circ}C$for 9 days without altering the sensitivity to saponins. Ginsenoside-Rb_1 did hemolysis, but Ginsenoside-Re protected erythrocytes from hemolysis. The following formula is proposed for calculation of saponins from ginseng extract: X=120$\mu$g $\times$$V_2/V_1$

• Bulletin of the Korean Chemical Society
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• v.12 no.1
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• pp.67-70
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• 1991

A hexagonal hexamer of water cluster is optimized by ab initio method using the 4-31G basis set. At this geometry the nonadditive many-body interactions are calculated. The ab initio calculation with large basis set [T. H. Dunning, J. Chem. Phys., 53, 2823 (1970); 54, 3958 (1971)] shows that a pentagonal unit is rather stable among several kinds of clustering units of water molecules.

• Journal of the Korean Magnetic Resonance Society
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• v.16 no.1
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• pp.78-90
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• 2012

To understand the electronic structure of $[NiS_4]^-$ complex ions, two complexes with such $[NiS_4]^-$ core, $FcCH=CHPymCH_3[Ni(dmit)_2]$ (Pym = pyridinium, $dmit^{2-}$ = 2-thioxo-1,3-dithiole-4,5-dithiolate) and $FcCH=CHPymCH_3[Ni(dddt)_2]{\cdot}{\frac{1}{2}}H_2O$ ($dddt^{2-}=5,6-dihydro-1,4-dithiin-2,3-dithiolato$), were synthesized to be characterized by X-ray crystallography, single crystal electron paramagnetic resonance (EPR) and density functional theory (DFT) calculation. Powder EPR spectra show narrow g-anisotropy but the anisotropy is bigger in $[Ni(dmit)_2]^-$ than in $[Ni(dddt)_2]^-$, indicating bigger spin density in Ni(III) d-orbital of $[Ni(dmit)_2]^-$ than in $[Ni(dddt)_2]^-$, which is consistent to DFT results. EPR studies of the crystals of the complexes surprisingly suggest that the $g_y$-axis of $[Ni(dddt)_2]^-$ is approximately on or perpendicular to the $[NiS_4]^-$ plane while the $g_y$-axis of $[Ni(dmit)_2]^-$ is on the plane, though DFT study of the complexes of this study and previously reported $[NiS_4]^-$ complexes indicate that the $g_y$-axis is on the $[NiS_4]^-$ plane.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.4
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• pp.558-564
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• 2021

With the recent introduction of 5G, electromagnetic radiation sources are spreading throughout life, so it is necessary to establish a citizen-centered electromagnetic safety management system. In particular, the beamforming method of the 5G antenna increases the power density measurement of electromagnetic waves by more than 10 times when the wireless base station is installed, so it is unreasonable to determine the safety by physical measurement. Therefore, it is necessary to determine the presence or absence of electromagnetic wave safety in daily life through a predictive method by calculation through systematic model analysis. In this paper, in order to check the possibility of a 5G wireless base station using an electromagnetic wave numerical analysis tool as a way to solve this problem, we compared the measured values of the actual base stations and the predicted values through the prediction model to compare the reliability. A method of constructing a real-time base station electromagnetic wave strength prediction evaluation system combined with software was also proposed.

• Journal of Korean Home Economics Education Association
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• v.6 no.1
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• pp.7-33
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• 1994

The purpose of this study is to revise the food composition table based on commonly consumed single serving size of cooked food so the people can easily use the table in each meal. With this revised food composition table, everybody can easily calculate how much they eat, and plan the menu according to how much they need, so hopely contribute to reduce the leftover foods. Eighty-nine kinds of prepared food dishes were selected based on 13 home economics text books of the junior and high schools. The results are summarized as follows: Cooked food dishes comprise various kinds of rice dishes, korean style soups and stewes, fried, roasted or steamed fishes, vegetables and meats, and desserts. Single serving size of cooked food dishes are presented below: 1) rise : 180∼250g, 1(1/3)∼1(2/3)cup 2)soup:320∼400g, 1(1/2)∼2cup 3)pan fried fish or vegetable : 40∼70g 4)deep fried vegetable, fish or meat; 60g 5)kimchi :50g Single serving size of all other dishes are presented based upon the most commonly consumed amount in each meal by adult male.

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1043-1046
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• 2013

Prediction of physicochemical properties of organic molecules is an important process in chemistry and chemical engineering. The MSEP approach developed in our lab calculates the molecular surface electrostatic potential (ESP) on van der Waals (vdW) surfaces of molecules. This approach includes geometry optimization and frequency calculation using hybrid density functional theory, B3LYP, at the 6-31G(d) basis set to find minima on the potential energy surface, and is known to give satisfactory QSPR results for various properties of organic molecules. However, this MSEP method is not applicable to screen large database because geometry optimization and frequency calculation require considerable computing time. To develop a fast but yet reliable approach, we have re-examined our previous work on organic molecules using two semi-empirical methods, AM1 and PM3. This new approach can be an efficient protocol in designing new molecules with improved properties.

• Transactions of Materials Processing
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• v.31 no.4
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• pp.200-206
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• 2022

The finite element analysis is one of the representative methods for predicting the materials behavior for experiments that are difficult to perform empirically. Constitutive equations are essential for reducing computation time and sharing data because they enable finite element analysis simulations through simple formulae. However, it is difficult to derive accurate flow curves for all materials as most constitutive equations are not formulated based on their physical meaning. Also, even if the constitutive equation is a good representation of the flow curve to the experimental results, some fundamental issues remain unresolved, such as the effect of mesh size on the calculation results. In this study, a new constitutive equation was proposed to predict various materials by modifying the combined Swift-Voce model, and the calculation results with various mesh sizes were compared to better simulate the experimental results.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3553-3560
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• 2010

A new hydrazone derivative compound has been synthesized and characterized by IR, $^1H$-NMR, $^{13}C$-NMR and UV-vis. spectroscopy techniques, elemental analysis and single-crystal X-ray diffraction (XRD). The new compound crystallizes in monoclinic space group C2/c. In addition to the crystal structure from X-ray experiment, the molecular geometry, vibrational frequencies and frontier molecular orbitals analysis of the title compound in the ground state have been calculated by using the HF/6-31G(d, p), B3LYP/6-311G(d, p) and B3LYP/6-31G(d, p) methods. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the observed experimental bands. To determine conformational flexibility, molecular energy profile of (1) was obtained by semi-empirical (AM1) calculation with respect to a selected degree of torsional freedom, which was varied from $-180^{\circ}$ to $+180^{\circ}$ in steps of $10^{\circ}$. Molecular electrostatic potential of the compound was also performed by the theoretical method.