• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3377-3385
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• 1994

This paper introduces empirical correlations to obtain the gas/liquid flow rates and the spray drop size of low viscosity liquid injected by Y-jet twin-fluid atomizers. The gas flow rate is well correlated with the gas injection pressure and the mixing point pressure, based on the compressible flow theory. Similarly, the liquid flow rate is determined by the liquid injection pressure and the mixing point pressure, and a simple correlation for the liquid discharge coefficient at the liquid port was deduced from the experimental results. The mixing point pressure, which is one of the essential parameters, was expressed in terms of the gas/liquid flow rate ratio and the mixing port length. Disintegration and atomization mechanisms both within the mixing port and outside the atomizer were carefully re-examined, and a "basic" correlation form representing the mean diameter of drops was proposed. The "basic" correlation was expressed in terms of the mean gas density within the mixing port, gas/liquid mass flow rate ratio and the Weber number. Though the correlation is somewhat complicated, it represents the experimental data within an accuracy of ${\pm}15%$.EX>${\pm}15%$.

• Journal of the Korean Data and Information Science Society
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• v.11 no.2
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• pp.173-179
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• 2000

Interval prediction based on the empirical distribution function for the class of time series with time varying coefficients is discussed. To this end, strong mixing property of the model is shown and results due to Fotopoulos et. al.(1994) are employed. A simulation study is presented to assess the accuracy of the proposed interval predictor.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2817-2822
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• 2007

The purpose of this paper is to study the influence of operating condition and ejector geometries on the hydrodynamics and on the mass transfer characteristic of ejector. The CFD results were validated with available experimental data. Flow field analyses and predictions of ejector performance were also carried out. Variation on the operating conditions was made by varying the gas-liquid flow rate ratio in the range of 0.2 to 1.2. The ejector configuration was also varied on the length to diameter ratio of mixing tube ($L_M/D_M$) in the range of 4 to 10. CFD studies show that at $L_M/D_M$ 5.5, the volumetric mass transfer coefficient increases with respect to gas flow rates. Meanwhile, at $L_M/D_M$ 4, the plot of volumetric mass transfer coefficient to gas-liquid flow rates ratio reach maximum at gas-liquid flow rates ratio of 0.6. This study also shows that volumetric mass transfer coefficient decrease with respect to the increase of mixing tube length.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.84-91
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• 2014

In this study, in order to find the improvement effect of metakaolin for using improvement of strength in concrete structures, it is investigated the diffusion coefficient of chloride ions and adiabatic temperature rise test. As a result, due to the mixing of metakaolin, it has been confirmed reducing diffusion coefficient of chloride ions and could prevent down of slump for use of adding fly ash. Therefore, ensuring resistance to chloride ion penetration into concrete, it is possible to enlarge the W/B ratio and reduce the adiabatic temperature rise by mixing of metakaolin. So, it is confirmed that the durability of concrete structures is increased.

• The Journal of the Acoustical Society of Korea
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• v.27 no.1
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• pp.26-32
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• 2008

UBSS (unde-determined blind source separation) is composed of the stages of BMMR (blind mixing matrix recovery) and BSR (blind source recovery). Generally, these two stages are executed using the sparseness of the observed data, and their performance is influenced by the accuracy of the measure of the sparseness. In this paper, as introducing the measure of the sparseness using the Gini coefficient to BSR stage, we obtained more accurate measure of the sparseness and better performance of BSR than methods using the $l_1$-norm, $l_q$-norm, and hyperbolic tangent, which was confirmed via computer simulations.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.6
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• pp.49-57
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• 2015

This paper presents the discharge characteristics and economic feasibility of a Dry $Air/O_2$ and a $N_2/O_2$ mixture gas in order to review $SF_6$ alternative. From AC discharge experiment in an quasi-uniform field, it was found that the optimal $N_2/O_2$ mixing ratio which breakdown voltage and surface flashover voltage were the highest was 70/30 and that the pressure dependence on the breakdown voltage was higher than that of the surface flashover voltage in the Dry $Air/O_2$ and the $N_2/O_2$ mixture gas. The mixing ratio (70/30) and the tendency of the pressure dependence were described in detail based on physical factors (impact ionization coefficient, electron attachment coefficient, secondary electron emission coefficient) involved in discharge mechanism and a electron source, respectively. In addition, the performance insulation and the economic feasibility of the Dry $Air/O_2$ and the $N_2/O_2$ mixture gas were discussed so that Dry $Air/O_2$ mixture gaswas more suitable than $N_2/O_2$ mixture gas to the $SF_6$ alternative.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.3
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• pp.323-333
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• 2014

In this paper, the wakes behind a square cylinder were simulated using two kinds of different turbulence models for the eddy viscosity concept such as the zero- and the one-equation model in which the former is the mixing length model and the latter is the k-equation model. For comparison between numerical and analytical solutions, we employed three skill assessments: the correlation coefficient(r) for the similarity of the wake shape, the error of maximum velocity difference(EMVD) for the accuracy of wake velocity and the ratio of drag coefficient(RDC) for the pressure distribution around the structure. On the basis of the numerical results, the feasibility of each model for wake simulation was discussed and a suitable value for the empirical constant was suggested in these turbulence models. The zero-equation model, known as the simplest turbulence model, overestimated the EMVD and its absolute mean error(AME) for r, EMVD and RDC was ranging from 20.3 % to 56.3 % for all test. But the AME by the one-equation model was ranging from 3.4 % to 19.9 %. The predicted values of the one-equation model substantially agreed with the analytical solutions at the empirical mixing length scale $L=0.6b_{1/2}$ with the AME of 3.4 %. Therefore it was concluded that the one-equation model was suitable for the wake simulation behind a square cylinder when the empirical constant for eddy viscosity would be properly chosen.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.3
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• pp.409-416
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• 2022

This paper relates to the blind noise separation method of time-delayed convolutive mixed signals. Since the mixed model of acoustic signals in a closed space is multi-channel, a convolutive blind signal separation method is applied and time-delayed data samples of the two microphone input signals is used. For signal separation, the mixing coefficient is calculated using an inverse model rather than directly calculating the separation coefficient, and the coefficient update is performed by repeated calculations based on secondary statistical properties to estimate the speech signal. Many simulations were performed to verify the performance of the proposed blind signal separation. As a result of the simulation, noise separation using this method operates safely regardless of convolutive mixing, and PESQ is improved by 0.3 points compared to the general adaptive FIR filter structure.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.4
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• pp.44-50
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• 1999

For the prediction of combustion performance of the Unlike Impinging Quadlet Injector (OOOF type), mixing efficiency, mixing characteristic velocity, and efficiency of mixing characteristic velocity were obtained from the cold test. Water/kerosene were used for simulants, The momentum ratio of oxidizer and fuel were mixing correlating parameter. Orifice discharge coefficient, spray pattern and mass distribution were measured. As a result, invasion-depth had strong effect on mixing efficiency, mixing characteristic velocity, and efficiency of mixing characteristic velocity. Mixing efficiency and efficiency of mixing characteristic velocity showed maximum value for momentum ratio 1.67(TMR = 2.5), and fuel rich state showed larger decreasing ratio than oxidizer rich state.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.1
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• pp.90-99
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• 2015

This study examined dynamic and characteristics and chloride penetration of concrete mixed with large amount of FA and BFS, which are considered for positive application to construction fields with purpose of long-tern durability of concrete structures. As a result of strength test on FA and BFS, FA concrete showed higher increase of strength compared to OPC, when FA4000 and FA5000 were mixed 30%, respectively. For BFS concrete, those mixed with 30% and 50% of BFS8000, respectively, showed higher or equivalent strength compare to OPC. As a result of test of chloride penetration on FA and BFS, diffusion coefficients of concrete mixed with 30% FA4000 and FA5000, respectively, showed to restrain average 6.5% of diffusion coefficient compared to OPC. And in case of BFS concrete, those mixed with BFS6000 and BFS8000, restrained diffusion of chloride ions 253% and 336%, respectively, compared to OPC. Therefore, Mixing 50% of BFS was most efficient in order to maximize restraint of chloride penetration according to metathesis of large amount. For relation between compression strength and diffusion coefficient of FA and BFS concrete, as strength increased, diffusion coefficient decreased. In this study, when mixing FA and BFS to concrete for long-run durability and restraint against chloride penetration, for FA, mixing it to concrete with less or equivalent 30% of replacement rate was most efficient. And for BFS, as fineness was higher and mixing it to concrete with less or equivalent 50% of replacement rate, there were results of higher strength compared to OPC and more efficient restraint of chloride ions.