• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.36-39
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• 2003

In this study, we made the high strength light weight concrete which was composed of the garnet minute powder to be the industry by-product in the YoungJoo region and the artificial light weight aggregate which the high temperature(1100℃) plastic process. The characteristic of the autogenous shrinkage had been considered about strength characteristic and the age passage In the following addition: The concrete's each unit quantity was determined 145,160,175㎏f/㎥.w/b and s/a was determined 30%, 43%, 45%. the each garnet's substitution ratio was determined 0, 10%. In this results, the compressive strength appeared greatly as the unit joining discretion grew bigger. The autogenous shrinkage ratio was increased rapidly until 7th day but it was reduced after 7th day regardless of the mixed factor. The autogenous shrinkage ratio which follows the change of the unit quantity and s/a increased together as the unit quantity and the s/a increases.

• Journal of the Korean Ceramic Society
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• v.23 no.1
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• pp.1-6
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• 1986

The shrinkage rate of solid state sintering has been theoretically derived by combining the rate equation of material transport and the net free energy change resulting from the decrease of solid-vapor interface and the increase of grain boundary during sintering. For a sinteing model an idealized situation of the spherical particles with BCC packing was taken as the initial condition and the shrinkage was assumed to occur by forming the flat circualr grain boundaries on each particle. The plotted shrinkage rates as a function of grain boundary to surface energy ratio $(gamma_g/gamma_s)$ have shown that the relative density increases linearly at the initial stage of sintering but the shrinkage rate is decreased upon further sintering due to a decrease in driving force for densificaton. It has been also shown that the densification is critically affected by the $gamma_g/gamma_s$ ratio. In order to get the complete densificatin the ratio should be less than $sqrt{3}$. Any additive or atmospheric condition causing the decrease of$_g/gamma_s$ ratio will enhance sintering.

• Journal of Environmental Science International
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• v.15 no.1
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• pp.77-84
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• 2006

An effective technique of sludge separation is required for excess sludge of sewage or wastewater plant. The separation of bulking sludge of paper manufacturing plant was studied using DAF(Dissolved Air Flotation) system. The effects of parameters such as nozzle type, A/S(air/solid) ratio. pressure, injection time of pressured water and saturation time were examined. The results showed that the best nozzle type was flat which had small orifice hole, The optimum A/S ratio and pressure were $7.070\times10^{-3}$(recycle ratio of pressured water $20\%$) and 5atm, respectively. Injection times of pressurized water around 20-25 sesc and flotation time of 30 min appeared to be optimal for the DAF operation. The order of performance of packing was 18 mm > 22 mm > 32 mm.

• Journal of Periodontal and Implant Science
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• v.43 no.5
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• pp.227-232
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• 2013

Purpose: The receptor activator of nuclear factor kappa B (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) system plays a significant role in osteoclastogenesis, activation of osteoclasts, and regulation of bone resorption. This study aimed to evaluate the use of the salivary soluble RANKL (sRANKL)/OPG ratio as a diagnostic marker for periodontitis in nonsmokers. Methods: Twenty-five patients with chronic periodontitis and 25 individuals with a healthy periodontium were enrolled in this study. Samples containing 5 mL of unstimulated saliva were obtained from each subject. Salivary sRANKL and OPG concentrations were determined using a standard enzyme-linked immunosorbent assay. Statistical analysis was performed using SPSS ver. 18.0. Results: The levels of sRANKL and OPG were detectable in all of the samples. Positive relationships were found between the plaque index and clinical attachment level and both the salivary concentration of sRANKL and the salivary sRANKL/OPG ratio (P<0.05). The salivary concentration of sRANKL and the sRANKL/OPG ratio were significantly higher in the periodontitis group than in the healthy group (P=0.004 and P=0.001, respectively). In contrast, the OPG concentration showed no significant differences between the groups (P=0.455). Conclusions: These findings suggest that the salivary sRANKL/OPG ratio may be helpful in the screening and diagnosis of periodontitis. However, longitudinal studies with larger populations are needed to confirm these results.

• Journal of Nutrition and Health
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• v.27 no.6
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• pp.574-582
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• 1994

The effects of age and dietary fatty acid composition on prostagladin production was investigated in Sprague-Dawley strain male rats. Animals weighing 88.6$\pm$2.2g were fed 10% dietary fat(W/W, 20% of total energy). The P/S ratios of dietary lipid were three levels(0.5, 1, 2) and there were three different levels of n-6/n-3 fatty acid ratio(2, 4, 8) in each P/S ratio. The experimental period were 1 month and 12 months, respectively. The results of this study were as follows. As the age of rats increased, the plasma thromboxane B2 production increased, but aorta 6-keto prostaglandin F1$\alpha$ decreased. When a higher amount of n-3 fatty acid was fed in each P/S ratio, the relative percentage of linolenic acid and EPA in platelet increased.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.75-76
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• 2018

MiDF, Micro Defect Free concrete, is the concrete made for high strength development by minimizing the defects such as micro pore and ITZ. Since MiDF exhibits strength through hydro-thermal synthesis reaction, it is essential to select the optimum C/S mole ratio. In this study, the basic characteristics of MiDF were evaluated by controlling the C/S mole ratio by SF and QP.

• Phonetics and Speech Sciences
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• v.4 no.3
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• pp.161-169
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• 2012

The purpose of this study was to investigate the characteristics of speech intelligibility of spontaneous speech and the vowel space parameters in patients with Parkinson's disease. Ten PD patients (M=5, F=5) and a corresponding control group of ten normal adults participated in this study. Firstly, subjects were asked to tell a story about their hometown and youth in order to analyze speech intelligibility. Secondly, the subjects were also asked to repeat four vowels (/a/, /i/, /u/, /e/) five times in order to compare their vowel spaces. The results were as follows: (1) the speech intelligibility of the PD group was lower than that of the control group. (2) Four parameters including vowel area, vowel articulatory index, formant centralization ratio, F2i/F1u ratio were significantly different in each group. For instance, vowel area and F2 ratio were wider and higher, respectively. As a result, a decrease in speech intelligibility of patients with PD is likely to show different types of errors from the normal group. The results of this research are meaningful in a sense that they could provide the objective standard of speech intelligibility and vowel space parameters.

• Current Photovoltaic Research
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• v.3 no.3
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• pp.75-79
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• 2015

Recently, $Cu_2ZnSn(S_xSe_{1-x})_4$ (CZTSSe) has been received a tremendous attraction as light absorber material in thin film solar cells (TFSCs), because of its earth abundance, inexpensive and non-toxic constituents and versatile material characteristics. Kesterite CZTSSe thin films were synthesized by sulfo-selenization of sputtered Cu/Sn/Zn stacked metallic precursors. The sulfo-selenization of Cu/Sn/Zn stacked metallic precursor thin films has been carried out in a graphite box using rapid thermal annealing (RTA) technique. Annealing process was done under sulfur and selenium vapor pressure using Ar gas at $520^{\circ}C$ for 10 min. The effect of tuning Se/(S+Se) precursor composition ratio on the properties of CZTSSe films has been investigated. The XRD, Raman, FE-SEM and XRF results indicate that the properties of sulfo-selenized CZTSSe thin films strongly depends on the Se/(S+Se) composition ratio. In particular, the CZTSSe TFSCs with Se/(S+Se) = 0.37 exhibits the best power conversion efficiency of 4.83% with $V_{oc}$ of 467 mV, $J_{sc}$ of $18.962mA/cm^2$ and FF of 54%. The systematic changes observed with increasing Se/(S+Se) ratio have been discussed in detail.

• Steel and Composite Structures
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• v.21 no.4
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• pp.921-947
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• 2016

Concrete Filled Fibre Reinforced Polymer Tube (CFFT) for new columns construction has attracted significant research attention in recent years. The CFFT acts as a formwork for new columns and a barrier to corrosion accelerating agents. It significantly increases both the strength capacity (Strength enhancement ratio) and the ductility (Strain enhancement ratio) of reinforced concrete columns. In this study, based on predefined selection criteria, experimental investigation results of 134 circular CFFT columns under axial compression have been compiled and analysed from 599 CFFT specimens available in the literature. It has been observed that actual confinement ratio (expressed as a function of material properties of fibres, diameter of CFFT and compressive strength of concrete) has significant influence on the strength and ductility of circular CFFT columns. Design oriented models have been proposed to compute the strength and strain enhancement ratios of circular CFFT columns. The proposed strength and strain enhancement ratio models have significantly reduced Average Absolute Error (AAE), Mean Square Error (MSE), Relative Standard Error of Estimate (RSEE) and Standard Deviation (SD) as compared to other available strength and strain enhancement ratios of circular CFFT column models. The predictions of the proposed strength and strain enhancement ratio models match well with the experimental strength and strain enhancement ratios investigation results in the compiled database.

• Korean Journal of Child Studies
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• v.38 no.1
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• pp.117-126
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• 2017

Objective: The purpose of this study was to investigate young children's nonsymbolic magnitude comparison ability according to ratio limit and task condition. Methods: The participants included 40 3-year-old children, 42 4-year-old children, and 41 5-year-old children recruited from 4 childcare centers located in Seoul, Korea. All magnitude comparison tasks were composed of image material tasks and concrete material tasks. In addition, each magnitude comparison task varied with the ratio of the two quantities; 0.5 ratio, 0.67 ratio, 0.75 ratio. Results and Conclusion: The results revealed that 3-, 4-, and 5-year-old children could perform nonsymbolic magnitude comparison tasks without learning experiences. Also, 3-, 4-, and 5-year-old children could perform concrete material tasks better than image material tasks in nonsymbolic magnitude comparison tasks. Furthermore, children's performance on nonsymbolic magnitude comparison tasks indicated the ratio signature of the approximate number system. Children have a degree of numerical capacity prior to formal mathematics instruction. Also, children were influenced by task conditions or sense stimulus when they processed numerical information. Furthermore, the approximate number system can be used in understanding the ordinality of number.