• Journal of ILASS-Korea
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• v.27 no.1
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• pp.26-35
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• 2022

Electrospray is a method of atomizing fluid using high voltage supply and capable of generating continuous flow and coherent size of droplets. Electrical system and properties of fluids has enabled electrospray to have various spray modes. However, its studies have been confined only in Cone jet, which is more stable and easier to manipulate droplets' size than other spraying modes. Therefore, it is necessary to investigate and compare other spraying modes based on experimental parameters and physical properties of fluids. This research paper identified nine different spray modes. It was found out that Sauter Mean Diameter (SMD) is proportional to flow rate of fluids and maximum difference among spray modes was 1.7 times. On the other hand, SMD standard deviation had low variations on specific flow rates of fluids. Pulsed jet mode recorded the largest SMD standard deviation, while Spindle recorded the lowest.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.5
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• pp.72-79
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• 2003

Spray characteristics were investigated by impinging F-O-O-F type injector with varying the impingement angle through 15, 20 and 30 degree and the mixture ratio(O/F ratio) from 1.5 to 3.0. Experimental results show that the correlation between dispersion and impingement angle is not influenced of the mixture ratio variation, but which has influence on number density, and there is a linear correlation between dispersion and impingement angle. Velocity distribution, standard deviation and SMD of droplets are decreased as the impingement angle increases. Also, it was confirmed that the distribution of droplet size are in accordance with Rosin-Rammler and Upper-limit distribution.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1793-1803
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• 2010

The weighting method and goal programming require weighting factors or target values to obtain a Pareto optimal solution. However, it is difficult to define these parameters, and a Pareto solution is not guaranteed when the choice of the parameters is incorrect. Recently, the Mahalanobis Taguchi System (MTS) has been introduced to minimize the Mahalanobis distance (MD). However, the MTS method cannot obtain a Pareto optimal solution. We propose a function called the skewed Mahalanobis distance (SMD) to obtain a Pareto optimal solution while retaining the advantages of the MD. The SMD is a new distance scale that multiplies the skewed value of a design point by the MD. The weighting factors are automatically reflected when the SMD is calculated. The SMD always gives a unique Pareto optimal solution. To verify the efficiency of the SMD, we present two numerical examples and show that the SMD can obtain a unique Pareto optimal solution without any additional information.

• Journal of The Korean Society of Grassland and Forage Science
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• v.36 no.3
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• pp.248-256
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• 2016

The present study investigated the effect of enzyme inclusion on silage quality using meta-analysis tool. A total of 16 research papers reporting the effect of enzyme application on silage quality were employed in the meta-analysis of this study. Mixed model for integrating quantitative results from multiple studies was used first to calculate the predicted error of each study. Individual error from the estimated model was the applied into standard deviation of each study to calculate the mean difference. Finally, summary effect was determined using standard mean difference (SMD) and inversed variance weighting. Mixed model analysis and SMD analysis showed the same effect patterns in all analysis items. Enzyme inclusion in silage significantly (p < 0.05) altered all silage quality characteristics investigated compared to control when enzyme was not included. Our results showed that enzyme treatment increased dry matter content, preserved crude protein effectively, and elevated water soluble carbohydrate content. However, the pH value, acetic acid, propionic acid, neutral detergent fiber, and acid detergent fiber contents in silage with enzyme inclusion were lower than those of the control.

• Journal of Mechanical Science and Technology
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• v.16 no.5
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• pp.732-742
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• 2002

This paper presents twin spray characteristics of two impinging F-O-O-F type injectors in which fuel and oxidizer impinge on each other to atomize under the various conditions. The droplet size and velocity in the impinging spray flow field were measured using PDPA. The droplet size and velocity were investigated at the mixture ratios of 1.5, 2.0, 2.47 and 3.0 for four injectors in which two single F-O-O-F injectors were arranged at the intervals of 20.8, 31.2, 41.6 and 62.4mm respectively. In general, the arithmetic mean diameter, SMD and standard deviation of droplet size in the interaction area (X=0 and Y=0mm) were smaller, while the axial velocity in the interaction area was slightly higher. An empirical correlation is obtained for the (D$\_$10/)$\_$D//(D$\_$10/)$\_$c/ value under the assumptions of two identical droplets and these with different size and velocity. The droplets with low Weber numbers below 40 have possibility to coalesce, while those over 40 tend to disintegrate after impingement in the interaction area.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.758-763
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• 2001

This paper presents twin spray characteristics of two impinging F-O-O-F type injectors in which fuel and oxidizer impinge on each other to atomize under the various conditions. The droplet size and velocity in the impinging spray flow field were measured using a PDPA. The droplet size and velocity were investigated at mixture ratios of 1.5, 2.0, 2.47 and 3.0 for four injectors in which two single F-O-O-F injectors were arranged at intervals of 20.8, 31.2, 41.6 and 62.4mm respectively. In general, the arithmetic mean diameter, SMD and standard deviation of droplet size in the interaction area (X=0 and Y=0mm) were smaller. The axial velocity in the interaction area was slightly higher. Considering the behavior of impinged droplets using the We number calculated by using the axial velocity instead of the relative velocity in line C in Fig. 1(b) for four injectors, it is consumed that the We number over 500 had the possibility to disintegrate, and the We number below 500 had it to cohere after impingement of twin spray. The results of this study can be used for the design of a nozzle for liquid propellant rockets.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.227-236
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• 2018

This study was conducted to define hippocampal volume differences between a stress-laid group and normal individual group via meta-analysis. This investigation included studies that contained hippocampal volume measurements in association with stress from 1990 to 2016. Magnetic resonance imaging (MRI) measurements of hippocampal volumes were used to determine the mean size, standard deviation and sample size. The pooled effect size was measured by the standardized mean difference (SMD) with a 95% confidence interval. This meta-analysis included 13 studies comprising 374 stress subjects and 439 normal subjects. Eight studies targeted war-related veterans and holocaust survivors, while five targeted personal trauma associated with childhood abuse, rape, accident or financial hardship. The overall mean effect size (Hedges' g) was -0.70 (-1.04; -0.37). Overall, the SMD value was -0.70, with a moderate effect size, but high heterogeneity. Depending on the characteristics of the stressor, studies were divided by subgroups of war-related veterans and subjects with personal trauma and then analyzed again. In the war-related subgroup, the Hedges' g was -0.47 (-0.78; -0.16), while in the personal stressor-related subgroup it was -0.91 (-1.57; -0.26). These results indicate that there was a significant negative correlation between psychological stress and hippocampal volume.

• International Journal of Korean Welding Society
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• v.5 no.1
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• pp.15-28
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• 2005

The ball shear test was investigated in terms of the effects of test parameters, i.e., shear height and shear speed, with an experimental and non-linear finite element analysis for evaluating the solder joint integrity of area array packages. Two representative Pb-free solder compositions were examined in this work: Sn-3.5Ag-0.75Cu and In-48Sn. The substrate was a common SMD type with solder bond pad openings of 460 $\mu$m in diameter. The microstructural investigations were carried out using SEM, and the IMCs were identified with EDS. Shear tests were conducted with the two varying test parameters. It could be observed that increasing shear height, at fixed shear speed, has the effect of decreasing shear force for both Sn-3.5Ag-0.75Cu and In-48Sn solder joints, while the shear force increased with increasing shear speed at fixed shear height. Too high shear height could cause some undesirable effects on the test results such as unexpected high standard deviation values or shear tip sliding from the solder ball. The low shear height conditions were favorable for screening the type of brittle interfacial fractures or the degraded layers in the interfaces. The shear speed conditions were discussed with the stress analyses of the solder ball, and we cannot find any conspicuous finding which is related to optimum shear speed from the stress analyses.