• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.3
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• pp.205-209
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• 2017

Unlike spherical drop impact, ellipsoidal drop impact can control the bouncing height on a heated surface by significantly altering impact behavior. To scrutinize the effect of the aspect ratio (AR) of the drop on the bounce suppression, in this study, non-axisymmetric spreading behaviors are observed from two side views and characterized based on the spreading width of the drop for horizontal principal axes. In addition, the maximum spreading width is investigated for various ARs. The results show that as the AR increases, the maximum spreading width of the minor axis increases, whereas that of the major axis shows no significant variation. In the regime of high AR and high impact velocity, liquid fragmentations by three parts are observed during bouncing. These fragmentations are discussed in this work. The hydrodynamic features of ellipsoidal drop impact will help understand bouncing control on non-wetting surfaces for several applications, such as self-cleaning and spray cooling.

• Korean Chemical Engineering Research
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• v.44 no.3
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• pp.284-288
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• 2006

$(Ca,Sr)_{2-y}MgSi_2O_7:Eu^{2+}{_y}$ (CMS) phosphor particles were prepared by using a spray pyrolysis process. The luminescent property was optimized by changing the content of Eu and the post-treatment temperature. The luminescence characteristics were also monitored with changing the ratio of Ca to Sr. The pure tetragonal $Ca_2MgSi_2O_7$ or $Sr_2MgSi_2O_7$ particles were obtained when the post-treatment temperature was over $1,000^{\circ}C$. The highest emission intensity of CMS particles were achieved when the concentration (y) of Eu and the treatment temperature were 0.05 and $1,250^{\circ}C$,respectively. The emission wavelength $({\lambda}_{max})$ of ${(Ca_{1-x},Sr_x)}_{1.95}MgSi_2O_7:{Eu^{2+}}_{0.05}$ was gradually shifted from 524 nm to 456 nm with increasing the content of Sr due to the reduction of crystal field strength. The emission intensity and its width of $Sr_2MgSi_2O_7:Eu$ was greatly enhanced by substituting Ca of less than 10 mol％ for Sr without any significant peak shift. The morphology of as-prepared particles was spherical, but changed to irregular-shaped one after the post treatment at the temperature range from 900 at $1,300^{\circ}C$.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.26 no.6
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• pp.155-164
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• 2023

Sedirea japonica is one of the critically endangered species in South Korea mostly due to artificial harms such as illegal collection and habitat destruction. Therefore, artificial propagation through improving germination rate, increasing growth, and controlling flowering is meaningful for the conservation and reintroduction of S. japonica. It is suggested that cytokinins are one of the multi-factors that contribute to plant growth and floral responses. Especially, exogenous cytokinins have been known to induce or promote shoot growth or earlier flowering in orchids. Therefore, it was investigated how the application of 6-benzylaminopurine (BA) influenced the growth and inflorescence of S. japonica. A foliar spray containing BA at 100, 200, 300, and 400 ppm was applied from 1st July to 30th December 2021. Leaf length, leaf length growth rate, leaf width, and width and length ratio were measured as growth-related factors. Visible inflorescence rate, inflorescence length, the number of flowers per inflorescence, and the distance between the stalks were measured as flowering-related factors. Growth-related factors except for leaf growth rate were not affected by BA treatments, while leaf growth rate was significantly increased by 200 ppm of BA treatment. The visible inflorescence rate increased by 200 ppm of BA treatment, and there seems an optimal concentration and threshold of BA treatment. An iterative experiment with more seedlings and measurement factors would be helpful to figure out the effects of exogenous BA treatment on S. japonica, and it can be applied for mass propagation.

• Fire Science and Engineering
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• v.26 no.2
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• pp.75-83
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• 2012

An experimental study was conducted to investigate the effects of change in heat release rate on unsteady fire characteristics of under-ventilated fire in a semi-closed compartment. A standard doorway width of the full-scale ISO 9705 room was modified to 0.1 m and the flow rate of heptane fuel was increased linearly with time using a spray nozzle located at the center of enclosure. Temperature, heat flux, species concentrations and heat release rate were continuously measured and then global equivalence ratio (GER) concept was adopted to represent the unsteady thermal and chemical characteristics inside the compartment. It was observed that there was a significant difference in unsteady behavior between global and local combustion efficiency, and the GERs predicted by ideal and measured heat release rate were also shown different results in time. The unsteady behaviors of temperature, heat flux and species concentrations were represented well using the GER concept. It was important to note that CO concentration was gradually decreased with the increase in GER after reaching its maximum value in the range of 2.0~3.0 of global equivalence ratio. In addition, the experimental data on unsteady thermal and chemical behaviors obtained in a semi-closed compartment will be usefully used to validate a realistic fire simulation.

• Horticultural Science & Technology
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• v.34 no.2
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• pp.269-281
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• 2016

The statistical analyses of coefficient of variation, heritability, and genetic advance were carried out to identify differences in morphological characteristics, such as the stem and inflorescence length, of 10 major commercial cultivars of spray chrysanthemum (Chrysanthemum morifolium). For morphological characteristics, stem lengths ranged from 46.4 cm to 54.9 cm, the maximum diameter of stem was 5.6 to 8.5 mm, the hardness of the stem was 0.17 to $0.70kg{\cdot}m^{-2}$, the fresh weight of stem was 7.5 to 17.5 g, the dry weight of the stem was 1.6 to 3.3 g, the ratio of dry weight/fresh weight of stem was 15.9% to 23.1%. Also, the number of leaves on the stem was 8.4 to 12.2, the stem leaf area was 17.8 to $37.8m^2$, the fresh weight stem leaves was 5.3 to 18.6 g, the dry weight was 0.5 to 1.4 g and the ratio of dry weight /fresh weight of stem leaves was 7.6% to 11.5%. The inflorescence length ranged from 10.1 to 18.6 cm, the fresh weight of inflorescence was 7.3 to 26.7 g, the dry weight of inflorescence was 1.2 to 2.8 g, the ratio of dry weight /fresh weight of inflorescence was 10.4% to 17.1%. For flower, the diameter of the flower center was 8.2 to 13.3 mm, the petal width was 5.7 to 14.0 mm, the petal length was 12.9 to 33.1 mm, and the petal thickness was 157.8 to $354.4{\mu}m$. The mean values of each character in each cultivar were very different, and DMRT and LSD values based on morphological characteristics among 10 cultivars were highly significant. For variability and genetic parameters, the lowest CV (coefficient of variation), PCV (phenotypic coefficient of variation), and GCV (genotypic coefficient of variation) were 4.79% to 5.15% in stem length, and the highest variations were 62.97% to 65.21% in leaf area. ECV (error or environmental coefficient of variation) was the lowest for leaf area (1.71%) and it was the highest for leaf dry weight (19.30%). Heritability also significantly differed among the characteristics, ranging from 68.69% to 99.67%, the lowest value was shown in ratio of dry weight /fresh weight of stem and the highest value was for leaf area of stem. The value for genetic advance was the lowest in hardness of stem at 0.30 and the highest in leaf thickness at 156.65. The lowest genetic advance as percentage of mean of stem hardness was 9.17%, while the highest percentage of stem length was 134.27%. Thus the characters which had the highest values indicated above show the influence of additive gene action and may provide useful resources for selection programs for agronomic improvement.

• Journal of dental hygiene science
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• v.15 no.3
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• pp.259-264
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• 2015

For this experiment, specimen was manufactured by injecting polymer and monomer into silicon mold with volume ratio of 2.5:1 based on ISO 20795-2 so that average thickness, width and length of specimen would be maintained as 3.3 mm, 10.0 mm and 65.0 mm, respectively depending on spray on technique. Specimen was divided into 3 groups ($25^{\circ}C$, $40^{\circ}C$, $70^{\circ}C$) depending on polymerization temperature and 10 specimen was manufactured for each group and it was polymerized in water tank of ${\pm}1^{\circ}C$ under the setting condition of polymerization time of 15 minutes and pressure of 3 bar. After keeping specimen in distilled water of $37^{\circ}C$ for over 48 hours before experiment, flexural strength (FS) and elasticity modulus (EM) of specimen being tested by using Intron (3344; Instron; Instron). SPSS ver. 16.0 was used for analysis and post-hoc test of Scheffe was performed after using one-way ANOVA. When comparing mean value of FS of resin for orthodontics, it was represented in the range of 71.500 MPa for $25^{\circ}C$ group, 74.920 MPa for $40^{\circ}C$ group and 76.880 MPa for $70^{\circ}C$ group and difference was shown in the order of $25^{\circ}C$ group <$40^{\circ}C$ group <$70^{\circ}C$ group but such difference was not significant statistically (p=0.052). Result of EM mean value of resin for orthodontics was more polymerization temperature was high, the more was significant difference represented in the order of $25^{\circ}C$ group <$40^{\circ}C$ group <$70^{\circ}C$ group (p<0.039).