• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.972-977
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• 2017

The propellant tile and crack which account for the greatest proportion of solid rockets are profoundly affected by viscosity and mechanical properties of solid propellant. In this paper solid propellant with nitrate ester polyester(NEPE) system has been researched for the viscosity, mechanical properties and burning properties with size and mixing ratio of RDX. the viscosity of propellant was changed significantly depending on the size of RDX and mixing ratio, and mechanical properties of NEPE system propellant were also varied. Considering both lower viscosity and stable mechanical properties, the optimum size and mixing ratio of RDX can be identified as the main factors to the NEPE system propellant.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.369-372
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• 2000

ZnO varistor is studied to sintering condition and mixing condition for the improvement to non linear of electrical characteristics. In this paper, ZnO varistor, ZnO-Bi$_2$O$_3$-Y$_2$O$_3$-MnO-Cr$_2$O$_3$-Sb$_2$O$_3$series, is fabricated with Sb$_2$O$_3$mol ratio(0.5~4[mol%]) and sintered at 1250[$^{\circ}C$] for 2 hours. The grain size to Sb$_2$O$_3$moi ratio was measured by fractal mathematics. The ZnO varistors that Sb$_2$O$_3$mot ratio is 1[mol%] were shown small grain size because of spinel phase. The fractal dimension were increased with increasing of Sb$_2$O$_3$mo ratios. The capacitance of ZnO varistors with increasing of Sb$_2$O$_3$additive in voltage-capacitance characteristics was decreased by small grain size.

• Archives of Pharmacal Research
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• v.27 no.7
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• pp.797-805
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• 2004

LPD vectors are non-viral vehicles for gene delivery comprised of polycation-condensed plasmid DNA and liposomes. Here, we described a novel anionic LPD formulation containing protamine-DNA complexes and pH sensitive liposomes composed of DOPE and cholesteryl hemisuccinate (Chems). Central composite design (CCD) was employed to optimize stable LPD formulation with small particle size. A three factor, five-level CCD design was used for the optimization procedure, with the weight ratio of protamine/DNA ($X_1$), the weight ratio of Chems/DNA ($X_2$) and the molar ratio of Chems/DOPE in the anionic liposomes ($X_3$) as the independent variables. LPD size ($Y_1$) and LPD protection efficiency against nuclease ($Y_2$) were response variables. Zeta potential determination was utilized to define the experimental design region. Based on experimental design, responses for the 15 formulations were obtained. Mathematical equations and response surface plots were used to relate the dependent and independent variables. The mathematical model predicted optimized $X_1-X_3$ levels that achieve the desired particle size and the protection efficiency against nuclease. According to these levels, an optimized LPD formulation was prepared, resulting in a particle size of 185.3 nm and protection efficiency of 80.22％.

• Clinical and Experimental Pediatrics
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• v.64 no.1
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• pp.31-36
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• 2021

Background: The diagnosis of esophageal varices (EV) is based on the findings of esophagogastroduodenoscopy (EGD), biopsy, and serum markers. Thus, noninvasive cost-effective tests through which high-risk EV children can be diagnosed are needed. Purpose: This cross-sectional study aimed to identify the noninvasive markers for EV in children with liver cirrhosis. Methods: A total of 98 children with liver cirrhosis were evaluated in this study. The spleen size, platelet count, serum albumin, liver function test results, and risk scores were evaluated prior to endoscopy. The endoscopic investigations aimed to identify the presence of EV and red signs, and determine varices sizes. Results: Endoscopy revealed varices in 43 subjects (43.9%). The spleen size, platelet count, international normalized ratio, aspartate aminotransferase to platelet ratio index (APRI), platelet count to spleen size ratio, and risk score differed significantly between patients with and without EV on univariate analysis; however, the logistic regression analysis showed no differences, indicating that none of these parameters were independently associated with the presence of EV. Conclusion: Platelet count, risk score, platelet count to spleen size, and APRI can be useful tools for the identification of high-risk patients with EV and might reduce the need for invasive methods like EGD.

• Journal of the Korean Geotechnical Society
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• v.24 no.8
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• pp.125-135
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• 2008

Rigid-soft particle mixtures, which consist of sand and rubber, are investigated for the understanding of the stress-deformation and elastic moduli. Specimens are prepared with various size ratio sr between sand and rubber particles, and different volumetric sand fraction sf. Small strain shear waves are measured under $K_o$-loading condition incorporated with the stress-deformation test by using oedometer cell with bender elements. The stress-deformation and small strain shear wave characteristics of rigid-soft particle mixtures show the transition from a rigid particle behavior regime to a soft particle behavior regime under fixed size ratio. A sudden rise of $\Lambda$ factor and the maximum value of the $\zeta$ exponent in $G_{max}=\;{\Lambda}({\sigma}'_{o}/kPa)^{\zeta}$ are observed at $sf\;{\approx}\;0.4{\sim}0.6$ regardless of the size ratio sf. Transition mixture shows high sensitivity to confining stress. The volume fraction for the minimum porosity may depend on the applied stress level in the rigid-soft particle mixtures because the soft rubber particles easily distort under load. In this experimental study, the size ratio and volumetric sand fraction are the important factors which determine the behavior of rigid and soft particle mixtures.

• Korean Journal of Human Ecology
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• v.16 no.2
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• pp.407-419
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• 2007

The purpose of this study was to identify the effect of four clothing cues dot pattern size and ground field of color area ratio on dress's wearer image. The experimental materials developed for this study are a set of stimuli and response scales(The 7-point semantic). The stimuli were 30 color pictures manipulated with the combination of dot pattern size, dot pattern on background of color area ratio and neutral dress's using computer simulation. The subjects were 180 female undergraduates living students in Gyeong-nam. The result of this study are as follows: Image factor of the stimulus was composed of 5 different components (visibility, gracefulness, attractiveness, cuteness, womanly). Especially, Neutral color combination independently influenced the every components. In regarding the effect of interaction between each variable, the combination of dot pattern on background of color area ratio, dot pattern size on the combination had cuteness, womanly.

• Proceedings of the Korean Institute of Interior Design Conference
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• 2006.05a
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• pp.169-172
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• 2006

Korean Apartment Housing, which has been built up for short-time, represents as popular housing reflecting our unique cultural background, and recently the utility room in apartment housing has been changed to accept residents' needs, focusing on their improving life styles. At this point, the purpose of this study Is to analyze the characteristics of the utility room between 1995 and 2005 in order to grasp the current change of the utility space in Korean Apartment Housing. For this, this research investigated 176 samples, collected in 'Apartment Encyclopedia(2004)'. The major results of this study are as follows : 1) As the utility room gets bigger, the size and the ratio to the whole unit area are increased, however the ratio in small area is bigger than the ratio in other area. 2) According to time, the utility room tends to increase the size and the ratio to the whole unit area, and the Increasing tendency appears distinctively after 2002. 3) The utility room used to be located with rear balcony area, however, now it appears to be planned Independently with its unique function. 4) Currently, Second-Kitchen start to plan in the apartment housing.

• Journal of the Korean Society of Industry Convergence
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• v.5 no.3
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• pp.225-232
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• 2002

The purpose of this study is to find the mechanical properties of lightweight concrete using expanded clay. Thus, slump, air content, compressive strength, elastic modulus, tensile strength, length change ratio, unitweight change ratio and absorption of lightweight concrete have been investigated. The conclusions of this study are as follows ; 1. The loss of slump and air content of concrete increased as the expanded clay content increased and the size of coarse aggregate decreased. 2. The compressive strength of concrete using 100% expanded clay of 13, 19mm size at 28 days were respectively 282, $252kgf/cm^2$. 3. The elastic modulus and tensile strength of concrete decreased with increase of expanded clay content. 4. The length change ratio of concrete increased with the larger coarse aggregate size, and decreased with the increase of expanded clay content. 5. The unit weight of concrete decreased with the increase of expanded clay content, and the ratio of that was larger at the early age.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.211-212
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• 2011

It was very important to evaluate concrete experimentally at elevated temperature because concrete was filled with aggregate of concrete volume about 70 percent. Concrete exposure to high temperatures produces changes in its internal structure, for instance loss of its strength and deformation capacity, in extreme cases risking the service life of the structure. The work of this paper is performed to evaluate the thermal behavior of ultra-high strength concrete having different water to cement ratio (strength), fine aggregate to aggregate ratio and maximum size of coarse aggregate. For exposure to 500℃ during 1 hour, residual mechanical properties of the ultra-high strength concrete decreased as the s/a ratio decreases and the maximum size of coarse aggregate increases.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.185-189
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• 2000

ZnO varistor has many merits as compared with SiC varistor. But, because of leakage current and non-linear coefficient, it has unstable function properties. For the purpose of improvement of ZnO varistor properties, ZnO varistor is studied according to sintering condition and mixing condition. ZnO varistor, $ZnO-Bi_2O_2-Y_2O_3-MnO-Cr_2O_3-Sb_2O_3$ series, is fabricated with $Sb_2O_3$ mol ratio(0.5-4[mol%]) and sintered at $1250[^{\circ}C]$ In accordance with $Sb_2O_3$ mol ratio and sintering temperature, grain size and non-linear coefficient are measured. The specimen, $Sb_2O_3$ mol ratio is 1[mol%], has small grain size. It has best properties because of its liquid phase shape. When $Sb_2O_3$ mol ratio is 1[mol%], grain size is decreased.