• KSBB Journal
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• v.10 no.3
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• pp.298-303
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• 1995

Hydrogen peroxide has a characteristic of being dissociated rapidly into atomic oxygen and water when it is contacted with organic materials, resulting in a decrease in molecular weight of a polymer like carbohydrate. This effect on inulin hydrolysis under ultrasound irradiation was investigated. Maximum effect of hydrogen peroxide appeared at the H2O2 concentration of 2.3%(w/v) under the range of $50∼60^{\circ}C$ and 0.1∼0.3%(w/w) HCl. Compared to control reactions, the promotion effect reached 9∼43%. The activation energy, 26kca1/mo1, of inulin hydrolysis with H2O2 addition was similar to that without H2O2 addition, 25kca1/mo1. This implies that the rate enhancement of inulin hydrolysis with H2O2 addition is due to the increase of frequency factor.

• Journal of the Korean Ceramic Society
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• v.47 no.2
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• pp.136-141
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• 2010

ACF/ZnO photocatalyst was synthesized by a sol-gel method using activated carbon fiber (ACF) and Zn $(NO_3)_2$ as precursors. Samples were characterized by Brunauer-Emmett-Teller measurements (BET), scanning electron microscope (SEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDX). The XRD results showed that ACF/ZnO composites only included a hexagonal phase by heat-treated temperature at $400^{\circ}C$, $500^{\circ}C$, $600^{\circ}C$, and $700^{\circ}C$. The SEM analysis revealed that the ACF/ZnO composites did not exhibit any morphological changes of the catalyst surface according to the different heat-treated temperatures. The photocatalytic activity of the samples was tested for degradation of methylene blue (MB) solutions under ultraviolet (UV) light and ultrasonication respectively. The results showed that the photocatalytic activity of ACF/ZnO composites heat-treated at $500^{\circ}C$ was higher than other samples, which is ascribed to the fine distribution of ZnO particles on the surface of the ACF. In addition, an ultrasound of low power (50 W) was used as an irradiation source to successfully induce ACF/ZnO composites to perform sonocatalytic degradation of MB. Results indicated that the sonocatalytic method in the presence of ACF/ZnO composites is an advisable choice for the treatments of organic dyes.

• Journal of the Korean Society for Nondestructive Testing
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• v.16 no.4
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• pp.241-250
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• 1997

The velocity dispersion of surface acoustical wave(SAW) of Si layer/mesh Au/Si substrate was measured by the frequency analysis technique of backward radiation at liquid/solid interface. The difference of backward radiation patterns depending on used transducers (2, 5, 10MHz) confirmed that the backward radiation phenomenon was caused by the energy radiation from SAW generated in surface region. An ultrasonic goniometer was constructed to measure continuously the angular dependence of backscattered intensity. The angular dependences of backward radiation(5MHz) were measured for Ni layer/Al substrate specimens that were bonded by epoxy involving different content of Cu powder. It was known that the width and pattern of backward radiation had informations such as the velocity dispersion, bonding quality and structure of surface region.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.11
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• pp.2088-2092
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• 2011

The accelerated thermal aging of CSPE(chloro sulfonate polyethylene) of test cables were carried out for the period equal to 10, 20 and 30 years in air at $100^{\circ}C$, respectively. The CSPE cables(TAIHAN electric wire Co. Ltd) which installed in nuclear power plant for three years were used as starting materials. Condition monitering methods of the accelerated thermal aging of CSPE cables were estimated through indenter modulus and OIT(oxidation induction time) of IEC 62582, and those were newly estimated through volume electrical resistivity, ultrasound reflection time, density, FE-SEM(field emission scanning electron microscopy), XPS(x-ray photoelectron spectroscopy), EDS(energy dispersive spectroscopy), and WD-XRF(wavelength dispersive x-ray fluorescence). A new condition monitoring methods of the accelerated thermal aging of CSPE cables were generally coincident with trend of indenter modulus expect EDS, XPS and XRF. A volume electrical resistivity among new condition monitoring methods of the accelerated thermal aging of CSPE cables is excellent. It is considered that life-time of CSPE cable can be predicted through volume electrical resistivity, if CSPE jacket was aged for period such as more than 20 years.

• The Journal of the Acoustical Society of Korea
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• v.42 no.2
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• pp.143-151
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• 2023

In this paper, a method for evaluating the measurement uncertainty is proposed when measuring of floor impact sound insulation of buildings using standard heavy impact source. In addition to the effect of repeated measurements, several other factors such as measurement location, impact location, equipment used for sound pressure measurement, and heavy impact source, were considered. A mathematical model for the average maximum impact sound level and the uncertainty evaluation method for each factor were proposed. The present proposed method was applied to measurement results to evaluate the average maximum impact sound pressure level and the measurement uncertainty.

• Korean Journal of Community Nutrition
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• v.10 no.1
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• pp.91-100
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• 2005

This study was conducted to investigate the effects of smoking on nutrition intake, bone mineral density and blood mineral status. The subjects were composed of two groups: 100 smokers and 100 non-smokers was used along with a questionnaire. Anthropometric measurements, dietary intakes using 24-hours recall method were compared. At twenty subjects from each group were selected, bone mineral density were measured by quantitative ultrasound and plasma mineral levels were analyzed by ICP spectrometer. The average ages of smokers and non-smokers were 23.9 and 22.8 years old, respectively. The height, weight and BMI of the smokers were no significant difference. The average numbers of smoked cigarettes were 11.8/d and the average packyear was 3.1 in the smokers. About $97\%$ of the smokers drank alcoholic beverages, while $85\%$ of the non-smokers did. The smokers tended to eat less meals and dinner meal, but drink coffee more often compared to the non-smokers. The mean daily energy intake and CPF energy intake ratio were 2184. 9 kcal and 57.2 : 13.7 : 26.4 in the smokers and 2262.6 kcal and 55.8 : 13.1 : 28.6 in the non-smokers. The smokers consumed significantly lower intake of $\beta$-carotene. There were no significant differences in bone mineral density of BUA, SOS and QUI. There were no significant differences in plasma levels of Ca, Mg, Fe and Zn. However, plasma Cu level of the smokers was significantly higher than that of the non-smokers. In conclusion, the smokers of this study showed a more undesirable dietary intake in the light of their low ,B -carotene and high alcoholic beverages, and coffee. The plasma Cu level of the smokers was higher than that of the non-smokers, showing that Cu is involved in smoking. Therefore, it could be suggested that more systematic research be conducted with respect to Cu and smoking and that increased nutrition education and guidelines for smokers are required.

• Korean Journal of Community Nutrition
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• v.15 no.3
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• pp.393-402
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• 2010

The purpose of this study was performed to evaluate the prevalence of overweight and to compare the dietary behaviors, nutrient intake and physical activities of specialized game high school students. Total of 163 subjects participated and their weight, height, waist circumference, hip circumference and bone status by a quantitative ultrasound method were measured. The subjects were surveyed by a self-administered questionnaire about general characteristics, dietary behaviors and physical activities. Nutrient intakes of the subjects were assessed by semi-quantitative food frequency questionnaire. The subjects were divided into four groups on their obesity level by BMI. The prevalence of underweight, normal, overweight and obese group was 6%, 58%, 16%, and 20% respectively. BMI was negatively correlated with bone mineral density (p < 0.01) and positively correlated with WHR (p < 0.01). The dietary guideline compliance score for "Enjoy Korean rice food style" was 2.63, followed by "Prepare food sanitarily"2.48, "Do not skip breakfast"2.29, "Eat a variety of vegetables, fruits, dairy products daily"2.25, "Drink water instead of beverage"2.10, "Choose less fried foods"2.09 and "Maintain healthy weight"1.91. The exercise frequency of walking was not significantly different between groups; however, heavy exercise frequency was significantly lower in underweight group than the other groups (p < 0.05). The energy intake was 2153 kcal, which was 81.2% of the Estimate Energy Requirement, and the intake of calcium and vitamin $B_2$ was 66.7% and 77.8% of KDRIs. Particularly, the intake of iron, vitamin A and vitamin C was about 59.4%, 52.2% and 55.4% of KDRIs and INQ was 0.71, 0.63 and 0.65 respectively, and intake of folic acid fell behind 39.1% of KDRIs and INQ was 0.46. Our study suggests that the systematic and continuous nutrition education will have to be provided at schools to improve dietary and health behaviors and prevent chronic metabolic disease for students of specialized game high school.

• Journal of the East Asian Society of Dietary Life
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• v.15 no.6
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• pp.655-662
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• 2005

Body content bone mined density and nutrient intake status of 129 college women in Daegu area are analyze4 The mean age was 23.1 years. Bone mineral density was measured in their right heel by SONOST-2000 ultrasound bone densitometer, and nutrient intake was assessed by a Questionnaire. Diet intake data were obtained by using a 24 hours recall method to evaluate the subject's usual diet. The average energy, Ca, Ee, Zn and folate intakes were 64.2, 47.5, 54.7, 62.9 and $57.4\%$ of RDA, respectively. Ca/P and Ca/Protein ratio were 0.46 and 6.7, respectively. The mean adequacy ratio(MAR), an index of overall dietary quality wag 0.6. The index of nutritional quality was under 1.0 for protein(0.7), vitamin A(0.9), E(0.7), $B_1(0.8)$, niacin(0.8), $B_6(0.6)$ and phosphorus(0.6). The less the protein and energy intake, the less the bone mineral density(p<0.05). The intakes of protein(p<0.05) and that of phosphorus(p<0.001) were positively correlated with bone quality index(BQI). The calcium intake was positively correlated with Z-score(p<0.05). The phosphorus intake was positively correlated with T-score(p<0.001) and Z-score(p<0.0001). In conclusion, this study indicates that nutrient intake of the college women is considerably lower than the RDA. Also the BQI is lower than standard.

• Journal of Engineering Education Research
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• v.26 no.4
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• pp.22-35
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• 2023

As information and communication technology has developed remarkably, it has become possible to analyze various types of large-volume data generated at a speed close to real time, and based on this, reliable value creation has become possible. Such big data analysis is becoming an important means of supporting decision-making based on scientific figures. The purpose of this study is to develop a big data analysis tool that can analyze large amounts of data generated through engineering education. The tasks of this study are as follows. First, a database is designed to store the information of entries in the National Creative Capstone Design Contest. Second, the pre-processing process is checked for analysis with big data analysis tools. Finally, analyze the data using the developed big data analysis tool. In this study, 1,784 works submitted to the National Creative Comprehensive Design Contest from 2014 to 2019 were analyzed. As a result of selecting the top 10 words through topic analysis, 'robot' ranked first from 2014 to 2019, and energy, drones, ultrasound, solar energy, and IoT appeared with high frequency. This result seems to reflect the current core topics and technology trends of the 4th Industrial Revolution. In addition, it seems that due to the nature of the Capstone Design Contest, students majoring in electrical/electronic, computer/information and communication engineering, mechanical engineering, and chemical/new materials engineering who can submit complete products for problem solving were selected. The significance of this study is that the results of this study can be used in the field of engineering education as basic data for the development of educational contents and teaching methods that reflect industry and technology trends. Furthermore, it is expected that the results of big data analysis related to engineering education can be used as a means of preparing preemptive countermeasures in establishing education policies that reflect social changes.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.2
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• pp.84-89
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• 2006

A laser ultrasonic inspection system is a non-contact inspection device which generates and measures ultrasounds by using laser beams. A laser ultrasonic inspection system provides a high measurement resolution because the ultrasonic signal generated by a pulse laser beam has a wide-band spectrum and the ultrasonic signal is measured from a small focused spot of a measuring laser beam. In this paper, we have investigated the detection techniques of a surface-breaking crack by using the laser ultrasonic surface waves. A crack acts as a low pass filter whose cut-off frequency is lowered in proportion to the depth of a crack. And, the center frequency value of a spectrum is decreased in proportion to the depth of a crack. In this paper, we extracted the crack information by using the frequency attenuation from the normalized transfer function spectrum of a surface-breaking crack. Also, we effectively measured the crack depth by using the decreasing value of the center frequency from a crack passed ultrasonic signal. The proposed measuring techniques of crack depths provided more precise information than the amplitude measuring technique.