• The Korean Journal of Ceramics
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• v.3 no.2
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• pp.116-123
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• 1997

A chemically stabilized $\beta$-cristobalite, which is stabilized by stuffing cations of $Ca^{2+}$ and $Al^{3+}$, was prepared by a solution-polymerization route employing Pechini resin or PVA solution as a polymeric carrier. The polymeric carrier affected the crystallization temperature, morphology of calicined powder, and particle size distribution. In case of the polyvinyl alcohol (PVA) solution process, a fine $\beta$-cristobalite powder with a narrow particle size distribution (average particle size : 0.3$\mu\textrm{m}$) and a BET specific surface area of 72 $\m^2$/g was prepared by an attrition-milling for 1 h after calcination at 110$0^{\circ}C$ for 1h. Wider particle size distribution and higher specific surface area were observed for the $\beta$-cristobalite powder derived from Pechini resin. The cubie(P1-to-tetraganalb) phase transformation in polynystalline $\beta$-cristobalite was induced at approximately 18$0^{\circ}C$. Like other materials showing transformation toughening, a critical size effect controlled the $\beta$-to-$\alpha$ transformation. Densifed cristobalite sample had some cracks in its internal texture after annealing. The cracks, occurred spontaneoulsy on cooling, were observed in the sample with an average grain sizes of 4.0 $\mu\textrm{m}$ or above. In case of the sintered cristobalite having a composition of CaO.$2Al_2O_3$.40SiO$_2$, small amount of amorphous phase and slow grain growth during annealing were observed. Shear stress-induced transformation was also observed in ground specimen. Cristobalite having a composition of CaO.2Al2O3.80SiO2 showed a more sensitive response to shear stress than the CaO.$2Al_2O_3$.40SiO$_2$ type cristobalite. Shear-induced transformation resulted in an increase of volume about 13% in $\alpha$-cristobalite phase on annealing for above 10 h in the case of the former composition.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.1
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• pp.34-38
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• 2005

Effects of pH level and slurry particle size on material removal rate and planarization of langasite single crystal wafer have been examined. Higher material removal rate was obtained with lower pH level slurries while the planarization was found to be determined by average particle size of colloidal silica slurries. Slurries containing 0.045 ㎛ amorphous silica particles showed the best polishing effect without any scratches on the surface. Effective particle number has a strong effect on the surface planarization and the removal rate, so that the lower effective particle numbers produced low removal rate but the better planarization results.

• Journal of Sericultural and Entomological Science
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• v.16 no.2
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• pp.147-155
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• 1974

The purpose of this study is to find out influence of reeling conditions on the denier control of raw silk for automatic silk reeling machine. The results obtained are as follows： 1. Effect of groping end part temperature (X$_1$) (1) Average size Y＝0.02945X$_1$＋18.27 (2) Size range Y＝0.04224X$_1$＋2.99 (3) Size deviation Y＝0.01667X$_1$－0.13 (4) Maximum deviation of size Y＝0.04657X$_1$－0.929 (5) Quality of raw silk Y＝－0.07055X$_1$＋10.082. Effect of silk reeling bath temperature (X$_2$) (1) Average size Y＝0.0334X$_2$＋19.08 (2) Size range Y＝0.016X$_2$＋5.24 (3) Size deviation Y＝0.0014X$_2$＋1.05 (4) Maximum deviation of size Y＝0.0206X$_2$＋1.59 3. Effect of silk reeling velocity(X$_3$) (1) Size range Y＝0.01797X$_3$＋3.95 (2) Size deviation Y＝0.00327X$_3$＋0.845 (3) Maximum deviation of size Y＝0.00905X$_3$＋1.50 (4) Quality of raw silk Y＝－0.03232X$_3$＋8.62

• Korean Journal of Materials Research
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• v.28 no.10
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• pp.539-543
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• 2018

We report the structural, morphological and magnetic properties of the $Ni_{70}Mn_{30}$ alloy prepared by Planetary Ball Mill method. Keeping the milling time constant for 30 h, the effect of different ball milling speeds on the synthesis and magnetic properties of the samples was thoroughly investigated. A remarkable variation in the morphology and average particle size was observed with the increase in milling speed. For the samples ball milled at 200 and 300 rpm, the average particle size and hence magnetization were decreased due to the increased lattice strain, distortion and surface effects which became prominent due to the increase in the thickness of the outer magnetically dead layer. For the samples ball milled at 400, 500 and 600 rpm however, the average particle size and hence magnetization were increased. This increased magnetization was attributed to the reduced surface area to volume ratio that ultimately led to the enhanced ferromagnetic interactions. The maximum saturation magnetization (75 emu/g at 1 T applied field) observed for the sample ball milled at 600 rpm and the low value of coercivity makes this material useful as soft magnetic material.

• The Journal of Korean Academic Society of Nursing Education
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• v.27 no.1
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• pp.5-15
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• 2021

Purpose: This study aimed to provide a systematic review and meta-analysis of research on flipped learning effects applied to university students. Methods: The random effect model was applied to 21 papers to calculate the effect size. To verify the moderation effect, a meta regression analysis and meta ANOVA were performed. Publication bias was verified through a funnel plot, and then an Egger's regression test was conducted. Results: The overall average effect size was .69 (95% CI: .51-.87), showing a median effect size, which was statistically significant. The outcome variables were in the order of learning motivation (Hedges' g=.83), self-directed learning (Hedges' g=.78), learning achievement (Hedges' g=.66), and efficacy (Hedges' g=.50), which were statistically significant. Conclusion: Flipped learning was found to be statistically significant in improving self-directed learning, learning motivation, efficacy, and learning achievement amng university students. It is suggestd that this method be actively applied in university education.

• The Research Journal of the Costume Culture
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• v.24 no.2
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• pp.248-262
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• 2016

Most Korean companies in the fashion industry are SMEs, and the role of the CEO and management ownership is important for enhancing the firm's competence and developing strategies. The study aims to examine the effect of management ownership on company financial growth. In particular, the study focuses on the moderating effect of company age and size on Korean fashion SMEs' financial outcomes. Financial data based on company financial statements from 2012 to 2014 was collected by the Data Analysis, Retrieval and Transfer System of Korea's Financial Supervisory Service. A total of 295 companies' (domestic fashion businesses) data was analyzed by the bootstrap method. The median sales value in the financial year 2014 was 47,492,403,958 KRW, and the company size was divided by it. The companies were in business for an average of 20 years. According to the results, the management ownership had a negative effect on Compound Annual Growth Rate (CAGR) for the three-years, and the relationship between the two variables was moderated by company age. Additionally, the interaction effect of management ownership and company age on 3-CAGR was also moderated by company size. When the companies had spent only a few years in business, a negative effect of management ownership for small firms and a positive effect of management ownership on financial growth for medium firms were found. These results suggest that small companies starting business need to manage their company governance structure to make flexible decisions, and after retaining financial growth, the companies can expand their businesses based on strong ownership.

• Journal of the Korean Ceramic Society
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• v.30 no.4
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• pp.279-288
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• 1993

A study on calcination and reduction of AUC(ammonium uranyl carbonate, (NH4)4UO2(CO3)3) has been carried out by using TG-DTA in N2, air and H2 atmospheres, respectively. Phases of various intermediate obtained during thermal analysis of AUC in different atmospheres were confirmed by XRD. Powder characteristics of each intermediate were investigated by measuring particle size and specific surface area, and also observed by SEM. As a results, regardless of applied atmosphere AUC was calcined into amorphous UO3, which was converted to $\alpha$-U3O8 Via $\alpha$-UO3 in both H2 and N2 atmosphere, but directly into $\alpha$-UO3 in air atmosphere. Further reduction of U3O8 was only detectable in hydrogen atmosphere. During calcination and reduction, average particle size was reduced to less than 30% of original value without morphology change. Specific surface area was dramatically increased with release of NH3, CO2 and H2O from AUC powder and reached maximum value around 25$0^{\circ}C$, and then gradually decreased with the increase of temperature due to sintering effect of uranium oxides such as UO3 and U3O8. It was also found that the change of average crystallite size and pore size were closely related to the changes of specific surface area of uranium oxides.

• Journal of the East Asian Society of Dietary Life
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• v.9 no.1
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• pp.64-73
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• 1999

The purpose of this study was to estimate the effect of serving sizes on dish wastes, nutrient intake, and diet satisfaction for reduction of dish waste products. The dish waste, energy and protein intake, and satisfaction scores before and after dining were compared in 44 subjects fed various serving sizes(100%, 90%, 80% of standard size) of 10 frequently consumed Korean dishes. The result are as follows: 1. Average age, height, and weight of 44 subjects were 30.5, 174.0cm, and 68.1kg in men and 26.2, 164.2cm, and 53.5kg in women, respectively. 2. There was a significant difference in the dish waste rate of 10 Korean dishes to serving sizes. The range of dish waste rates of 10 Korean dishes was 13.14-33.04%. 3. The average energy intake from 10 Korean dishes in which 100% of the standard serving size was served was lower than Korean RDA. Protein intakes from Sulungtang, Yukgaejang, Deunjang-ggigae, and Bibimpab with 100% servins size, Soondubi-ggigae 90% servins size, and Galbitang, Bulgogi-bakpan, Sangsungui-bakpan, Bakpan 80% of standard serving size were higher than Korean RDA. 4. The satisfaction score before dining on Sulungtang, Bulgogi-bakpan, Sangsungui-bakpan decreased with decreasing serving size. However, there was no significant difference in satisfaction score after dining to serving size. These findings indicate that dish waste rate and diet satisfaction of 10 these Korean dishes are fixed and energy intake is insufficient. Therefore, for reduction of food waste and reasonable serving size of dishes evaluated in this study, there should be more studies about Korean menu development with decreasing serving size and increasing energy density.

• Computers and Concrete
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• v.33 no.2
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• pp.147-162
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• 2024

This study presents a random-aggregate mesoscale model integrating the random distribution of the coarse aggerates and the damage mechanics of the mortar and interfacial transition zone (ITZ). This mesoscale model can generate the random distribution of the coarse aggregates according to the prescribed particle size distribution which enables the automation of the current methodology with different coarse aggregates' distribution. The main innovation of this work is to propose the "correction factor" to eliminate the dimensionally dependent mesh sensitivity of the concrete damaged plasticity (CDP) model. After implementing the correction factor through the user-defined subroutine in the randomly meshed mesoscale model, the predicted fracture resistance is in good agreement with the average experimental results of a series of geometrically similar single-edge-notched beams (SENB) concrete specimens. The simulated cracking pattern is also more realistic than the conventional concrete material models. The proposed random-aggregate mesoscale model hence demonstrates its validity in the application of concrete fracture failure and statistical size effect analysis.

• 한국노년학
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• v.38 no.1
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• pp.65-82
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• 2018

The purpose of this study is to statistically summarize the effect sizes using meta-analysis of various Kigong programs implemented on the subject of physical health of the elderly. Including 23 academic journal studies and 11 thesis studies reported domestically until 2016, a total of 34 studies were selected and analyzed to verify the effect sizes of programs, program types, measuring variables, and activity elements. The findings are as follows. First, it was found that the programs were midium effective with overall average effect size showing .748(p<.001). A program of Tai-Chi indicated the largest effect size of .836(p<.001). In terms of measuring variables, physical strength showed the largest effect size of .806(p<.001). In terms of gender by group, it was found that groups consisting only of men indicated the largest effect size of 2.388(p<.001). As for effect size by group of disease state, normal group with showed the highest effect size of .804(p<.001). Second, in activity elements, 31~60 by the group size has the largest effect size of .873(p<.001), total number of sessions for 31~40 sessions indicated the largest effect value of .829(p<.001). As for number of sessions per week, 5 sessions showed largest effect value of .918(p<.001), in terms of activity time, 50 minutes showed large effect value of 1.391(p<.001). As summarized above, Kigong programs are midium effective for physical health of the elderly, as an activity elements to consider when configuring the program, for group size 31~60, 31~40 sessions in total, 5 sessions per week and 50 minutes per sessions were recommended.