• Composites Research
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• v.33 no.6
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• pp.336-340
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• 2020

In this study, carbon aerogels (CA) were prepared by sol-gel polycondensation of resorcinol and furfural in isopropanol using hexamethylenetetramine as a catalyst, and then directly drying the organic gels under isopropanol freeze-drying conditions, followed by carbonization under a nitrogen atmosphere. The preparation conditions of the CA were explored by changing the mole ratio of resorcinol to furfural. The effect of the preparation conditions on the pore structure of the CA was studied by nitrogen adsorption isotherms. The characteristics of the CA were studied by scanning and transition electron microscopy, and infrared spectrometry. The accessibility of pores and performance of the CA as an electrode in electric double layer capacitors were also electrochemically investigated. As a result, BET surface area and specific capacitance increased with the molar ratio of resorcinol to catalyst (R/C) ratio; the maximum values of 765 ㎡/g and 132 F/g were achieved at the R/C ratio of 200, respectively. Consequently, it was confirmed that increasing the R/C ratio increased the average pore size of the CA electrode, which improved the rate capability of the system.

• Clinical and Experimental Pediatrics
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• v.48 no.8
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• pp.857-864
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• 2005

Purpose : The objectives of this study was to evaluate the correlations between the indices of insulin sensitivity using fasting glucose and insulin level, and the body fat mass measured by bioelectrical impedance analysis(BIA) and dual energy X-ray absorptiometry(DEXA), and to determine the clinical usefulness of insulin sensitivity indices when obese children were followed up. Methods : In this study, 28 simple obese children and adolescents were included. Anthropometric data including body weight, height, obesity degree(OD), body mass index(BMI), and waist-to-hip ratio were collected and then body fat mass was measured by using BIA and DEXA. For metabolic data, 12 hour fasting serum glucose, insulin and lipid profiles were measured and indices for insulin sensitivity(G/I ratio, $log_{insulin}$, HOMA-IR, $log_{HOMA-IR}$, QUICKI) were calculated. Results : BMI had a higher correlation with insulin sensitivity indices than OD(G/I ratio, -0.463 vs -0.209; $log_{insulin}$, 0.417 vs 0.196; HOMA-IR, 0.301 vs 0.238; $log_{HOMA-IR}$, 0.403 vs 0.198; QUICKI, -0.451 vs -0.224). But OD had a higher correlation with body fat mass measured by BIA and DEXA than BMI(BIA, 0.612 vs 0.316; DEXA, 0.667 vs 0.512). The G/I ratio was correlated with body fat mass in BIA(r=-0.420, P<0.05) and DEXA(r=-0.512, P<0.01), percentage of body fat(percentage of fat) in BIA(r=-0.366, P<0.05) and DEXA(r=-0.449, P<0.01). HOMA-IR was only correlated with body fat mass in DEXA(r=0.341, P<0.05). Conclusion : This study revealed that G/I ratios had a statistically significant correlation with anthropometric obesity indices(OD and BMI) and also had a correlation with both body fat mass and percentage of fat. These results suggest that G/I ratios could be used as useful index when obese children and adolescence are followed up.

• Clinical and Experimental Pediatrics
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• v.53 no.9
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• pp.840-844
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• 2010

Purpose: Microalbuminuria is defined as increased urinary albumin excretion (30-300 mg/day) or microalbumin/creatinine ratio (30-300 mg/g) in a spot urine sample. Although microalbuminuria is a predictor of clinical nephropathy and cardiomyopathy, few studies have investigated microalbuminuria in children with urinary tract infection (UTI). Therefore, we compared the spot urine microalbumin/creatinine ratio in pediatric UTI patients with that of control subjects. Methods: We investigated the correlation between the ratio in children with UTI and age, height, weight, blood pressure, glomerular filtration rate (GFR), hematuria, vesicoureteral reflux, renal parenchymal defect, and renal scar, and its predictability for UTI complications. Results: We studied 66 patients (42 boys, 24 girls) and 52 healthy children (24 boys, 28 girls). The mean microalbumin/creatinine ratio in UTI patients was statistically significantly increased compared to the control group ($340.04{\pm}321.36mg/g$ vs. $225.68{\pm}154.61mg/g$, $P$=0.0141). The mean value of spot urine microalbumin/creatinine ratio ($384.70{\pm}342.22mg/g$ vs. $264.92{\pm}158.13mg/g$, $P$=0.0341) in 1-23 months age patient group showed statistically significant increase compared to control group. Microalbumin/creatinine ratio showed negative correlation to age (r=-0.29, $P$=0.0167), body surface area (BSA) (r=-0.29, $P$=0.0173) and GFR (r=-0.26, $P$=0.0343). The presence of hematuria ($P$=0.0169) was found to be correlated. Conclusion: The spot urine microalbumin/creatinine ratio in children with UTI was significantly greater than that in normal children, and it was positively correlated with GFR. This ratio is a potential prescreening and prognostic marker in UTI patients. Further studies are required to validate the predictability of microalbuminuria in pediatric UTI patients.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.8
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• pp.1185-1191
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• 2008

The core design technology for the multi-effect desalination plant using the thermo compressor (MED-TVC) was investigated by the performance test of multi effect desalination plant in this paper. The final G.O.R (gain of output ratio) of MED-TVC type desalination plant is strongly affected by the performance of thermo-vapor compressor. The present experiments for the desalinating capacity and G.O.R were obtained for the range of the motive steam pressure, 266.0, 250.0, 230.0 and 200.0 kPa. And as a practical problem, to investigate the influence of the sea water temperature to the G.O.R, the inlet steam temperature of the suction water vapor was changed in the range of $311.2{\sim}324.2$ K in the present experiment. Through the experiments, the maximum value of G.O.R was 8.5 at the condition of the motive steam pressure, 136.0 kPa and the minimum value of G.O.R was 8.1 at the condition of the motive steam pressure, 266.0 kPa. And it was confirmed that the range of desalination capacity was $355.2{\sim}264.0$ ton/day in the normal operation condition.

• Elastomers and Composites
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• v.49 no.3
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• pp.225-231
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• 2014

In this study, we used polypropylene grafted with itaconic acid (PP-g-IA) as a compatibilizer to prevent phase separation phenomenon which occurs upon blending polypropylene (PP) and ethylene-vinyl alcohol copolymer (EVOH). A compatibilizer was prepared using graft copolymerization of itaconic acid (IA) onto PP where input ratio of IA was 1, 2, 5, and 10 wt.%. To confirm the structure of PP-g-IA and the graft ratio of IA onto PP, we used $^1H$ NMR and FT-IR. We tested the compatibilizer which has highest graft ratio of 1% in immiscible PP/EVOH blends. The morphologies of PP/PP-g-IA/EVOH blends were analyzed by SEM. Thermal and mechanical properties of the blends were analyzed by DSC and UTM. PP-g-IA enhanced the interfacial adhesion of PP and EVOH copolymer.

• The Journal of the Petrological Society of Korea
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• v.25 no.1
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• pp.13-27
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• 2016

The characteristics of the rock cleavage inherent in Jurassic granite from Geochang were analysed. The phases of distribution of microcrack spacings were derived from the enlarged photomicrographs(${\times}6.7$) of the thin section. The evaluation for the six directions of rock cleavages was performed using nine parameters such as (1) frequency of microcrack spacing(N), (2) frequency ratio(${\leq}1mm$ and 4 mm >) to total spacing frequency(N:191), (3) spacing ratio(${\leq}1mm$) to total spacing(118.49 mm), (4) mean spacing($S_{mean}$), (5) difference value($S_{mean}-S_{median}$) between mean spacing and median spacing($S_{median}$), (6) density of spacing, (7) median spacing, (8) reduction ratio of spacing frequency to length frequency and (9) magnitude of exponent(${\lambda}$ and b) related to the distribution type of diagram. Especially the close dependence between the above spacing parameters and the parameters from the spacing-cumulative frequency diagrams was derived. The results of correlation analysis between the values of parameters for three rock cleavages and those for three planes are as follows. The values of (I) parameters(1, 2 and 3), (II) parameters(4, 5 and 6), (III) parameter(7), (IV) parameter(8) and (V) parameter(9) show the various orders of H(hardway, H1+H2) < G(grain, G1+G2) < R(rift, R1+R2), R < G < H, R < H < G, G < H < R and H < G < R, respectively. On the contrary, the values of the above four groups(I~IV) of parameters for three planes show reverse orders. This type of correlation analysis is useful for discriminating three quarrying planes. Six spacing-cumulative frequency diagrams were arranged in increasing order on the value of main parameter($S_{mean}-S_{median}$). These diagrams show an order of R2 < R1 < G2 < G1 < H2 < H1 from the related chart. In other words, the above six diagrams can be summarized in order of rift(R1+R2) < grain(G1+G2) < hardway(H1+H2). These results indicate a relative magnitude of rock cleavage related to microcrack spacing. Especially, the above main parameter could provide advanced information for prediction the order of arrangement among the diagrams.

• Journal of Power System Engineering
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• v.1 no.1
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• pp.80-90
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• 1997

The purpose of this study is to evaluate the validity examination of the J-R curve characteristics for the nuclear reactor pressure vessel steels and Al alloys by the load ratio analysis. The results of the load ratio analysis are compared with those of the J-R curve which are obtained by the ASTM unloading compliance method. The crack length calculated by the load ratio analysis is agree well with the measured final crack length. The slope of the exponential J-R curve estimated by the load ratio analysis is slightly smaller than that by the ASTM unloading compliance method. The J-R curve obtained by the ASTM unloading compliance method is over-predicted and should be offsetted due to the initial negative crack. On the other hand, the load ratio analysis method can evaluate the J-R curve by only load-displacement curve without particular crack measurement equipment.

• Journal of Korea Foundry Society
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• v.10 no.4
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• pp.332-341
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• 1990

The structure and tensile properties of the unidirectionally solidified Al-33wt.%Cu alloy have been investigated. Casted Al-33wt.%Cu alloy was unidirectionally solidified with rates (R) between 1㎝/hr and 24cm/hr maintaining the thermal gradient(G) at solid-liquid interface, $32^{\circ}C/cm$ and $21^{\circ}C/cm$. The entectic struture was varied according to the growth condition(G/R radio). When G/R ratio was larger than $8.5{\times}10^3$ $^{\circ}C/cm^2/sec$ the lamellar structure was formed, and colony structure was formed when G/R ratio was smaller than $8.5{\times}10^3$ $^{\circ}C/cm^2/sec$. The interlamellar spacing(${\gamma}$) in the above alloy system was vaired with the growth rate(R) According to "${\gamma}^2{\cdot}R＝8.8{\times}10＾{-11}cm^2/sec$" relationship. The yield stress (${\sigma}$0.001) and UTS for samples in the as-grown condition increased with the interlamellar spacing decrease and the values corresponding to colony structure are lower than those corresponding to amellar structure with the same lamellar spacing. The yield stress for samples in aged condition did not change with the interlamellar spacing.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.3-6
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• 2009

This research is an experiment to examine on the realization of Natural Color using R, G, B LEDs and this experiment was performed to cover two different stages. 1) When Natural Color using R, G, B LEDs was realized without correction in first stage, all color(R, G, B, C, M, Y) series had highly range of error from 0.0200 to 0.1500. 2) When R, G, B of LEDs was mixed at the ratio of 1:4.5907:0.0601 for realization of white in second stage, white was not realized to excitation purity. The second stage was Performed based on the three primary colors theory found out by Thomas Young in England and Hermann Ludwig Ferdinand von Helmholtz in Germany.

• Journal of the Ergonomics Society of Korea
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• v.36 no.5
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• pp.535-543
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• 2017

Objective: This study was designed to identify factors affecting pilots' +Gz tolerance recovery from +Gz induced exhaustion. Background: +Gz tolerance of pilots has been considered as a crucial factor to fly the modern high performance fighter aircrafts. However, the factors affecting pilots' G-tolerance recovery from +Gz induced exhaustion have not been examined in the acceleration research community. Method: A centrifuge profile consisting of a high +Gz run for pilot's exhaustion and a low +Gz run for pilot's recovery and another high +Gz runs for pilot's second exhaustion was designed. The subjects' +Gz tolerance recovery ratio was measured by ratio of second high +Gz run time to the first high +Gz run time. The subjects' +Gz tolerance recovery rate was measured by dividing the subjects' +Gz tolerance recovery ratio by the low +Gz run time. The subjects' G-tolerance recovery rate was analyzed with respect to the subjects' personal factors including subjects' anthropometric and physiologic characteristics, flight time, flying aircraft type and so on. Results: The subjects' previous three-month flight hours (r=-0.336, p=0.039), six-month flight hours (r=-0.403, p=0.012) and one-year flight hours (r=-0.329, p= 0.044) correlated with the subjects' G-tolerance recovery rate. Conclusion: The subjects' G-tolerance recovery rate is clearly related to the subjects' previous flight hours. However, the subjects' anthropometric and physiologic characteristics do not show any statistically significant correlation with the subjects' G-tolerance recovery rate. Application: This research provides a safety critical insight to aviation community by identifying the factors to affect the gravity-induced loss of consciousness (GLOC) of pilots.