• Economic and Environmental Geology
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• v.32 no.1
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• pp.1-11
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• 1999

In the last decade, the supply of natural aggregates has been continuously increased due to the other types of aggregates. In general, aggregates constitute 70-80% of the total volume of concrete, so the quality of aggregates is main factor controlling physical characteristics of concrete. For this reason, physical properties of aggregate according to different rock types were studied. The majority of crushed aggregates is taken out of granite, gneiss, sandstone, andesite, basalt and so forth. The physical properties of these rock types were tested and most of them fell within the acceptable limit on the base of Korean standard regulation. The major lithology of the crushed aggregates is granite and gneiss, both of which are marked for more than 50% of total lithology thpes in Korea. A to the physical properties of granite, the high specific gravity coincides with low porosity, low absorption ratio, while the abrasion and soundness index show, in general, no specific trend. It has been assumed that slight differences of the physical properties of granite aggregates are related with those of the mineral composition, grain size, and so on. In comparison to granite, the physical properties of gneiss have little correlation one after another. This trend is related to different mineral composition, grain size and typical sheet fractures typically prevailing in the texture of gneiss. Spatial pattern of physical properties shows that high specific gravity of granite coincides only with low porosity and absorption ratio in all provinces except Cheolla province, and high specific gravity of gneiss coincides with low porosity and absorption ratio only in Cheolla and Gandwon provinces.

• Journal of radiological science and technology
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• v.44 no.4
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• pp.295-300
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• 2021

This study aims to present new chest AP examination exposure conditions through a study on the effect on image quality and patient dose by applying high tube voltage and scatter ray post-processing software during chest AP examination in digital radiography equipment. This study was used a human body phantom and in the chest AP position, the dosimeter was placed horizontally at the thoracic spine 6. The experiment was conducted by dividing into a low tube voltage (70 kVp, 400 mA, 3.2 mAs) group and a high tube voltage (100 kVp, 400 mA, 1.2 mAs) group. The collimation size (14″× 17″) and the source to image receptor distance(110 cm) were same applied to both groups. Radiation dose was presented to dose area product and entrance surface dose. Image quality was compared and analyzed by comparing the difference between the signal-to-noise ratio and the contrast-to-noise ratio of the image according to the application of the scatter ray post-processing software under each condition. The average value of the entrance surface dose in the low and high tube voltage conditions was 93.04±0.45 µGy and 94.25±1.51 µGy, which was slightly higher in the high tube voltage condition, but the dose area product was 0.97±0.04 µGy and 0.93±0.01 µGy. There was a statistically significant difference in the group mean value(p<0.01). In terms of image quality, the values of the signal-to-noise ratio and the contrast noise ratio were higher in the high tube voltage than in the low tube voltage, and decreased when the scattering line post-processing function was used, but the contrast resolution was improved. If there is a scatter ray post-processing function during chest AP examination, it is helpful to actively utilize it to improve the image quality. However, when this function is not available, I thought that applying a higher tube voltage state than a low tube voltage state will help to realize images with a large amount of information without changing the dose.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.1
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• pp.35-44
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• 2017

In this paper, we attempt to investigate the moderating effect of brand power on the effect of in-flight service quality on customer satisfaction and recommendation in the aviation industry. The results were as follows. First, in the case of high brand power FSC(full service carriers), the cost-to-benefit ratio as well as all other flight service properties influence to customer satisfaction. However, in the case of low brand power FSC, the cost-to-benefit ratio showed a greater impact of customer satisfaction compared to other in-flight services. Second, as in the case of customer satisfaction, while the cost-to-benefit ratio more influence to customer recommendation than other in-flight services in low brand power FSC, the cost-to-benefit ratio as well as all other flight service properties influence to customer recommendation together in high brand power FSC. Therefore, low brand power FSC required tit-for-tat strategy against to LCC(low cost carriers) by pursuing disruptive innovation for price. And high brand power FSC required sustaining innovation strategy through improving flight services.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2008.04a
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• pp.192-194
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• 2008

The study has focused on the dyeing properties of 4 kinds of high temperature type mono azo disperse dyes, widely used in the dyeing factory, under the ultra low liqour ratio (1:4) dyeing condition. Among those, C.I. Disperse Red 343 and C.I. Disperse Blue 79 showed un-levelled dyeing results from the ultra low liquor ratio dyeing bath as well as poor dispersion stability under the high temperature. We recommended some leveling agents to improve the leveling behavior of these dyes mentioned above. The milling technology should be further developed to achieve the dispersion stability.

• Journal of the Korean Society of Physical Medicine
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• v.15 no.1
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• pp.11-18
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• 2020

PURPOSE: This study was to investigate examined the differences in the autonomic nervous functions of elite female judo athletes according to their performance by measuring the heart rate variability (HRV). METHODS: Sixteen elite female judo players participated in this study. The participants were divided into a high performance and low performance group according to the results of their competitions. The HRV (mean heart rate, SDNN, RMSSD, TP, LF, HF, LF/HF ratio) was measured in the resting status. A t-test was used to compare the two groups, and bivariate logistic regression analysis was performed to determine the HRV elements that affect performance. The data were analyzed using IBM SPSS Statistics ver. 24.0 (IBM Co., Armonk, NY, USA). RESULTS: The mean heart rate was higher in the high performance group (72.88) than in the low performance group (64.75) (p=.049). The LF/HF ratio was higher in the high performance group (3.43) than in the low performance group (0.83), and the results were significant (p=.038). No HRV elements having a significant effect on the performance were observed. CONCLUSION: This study showed that the activity of the sympathetic nervous system was dominant in the high performance group in the resting status than in the low performance. The high performance group is believed to be in the overtraining status who experience more stress.

• 한국노년학
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• v.41 no.1
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• pp.127-147
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• 2021

It is critical to secure stable financial resources and efficient financial management for local governments to promote elderly welfare. Using the Fuzzy Set Qualitative Comparative Analysis method, we empirically examined the conditions under which the 17 metropolises and provinces in Korea increase or decrease their budget for elderly welfare. After examining previous studies, socio-economic variables(ratio of elderly people, ratio of elderly welfare recipients), financial variables(financial independence ratio), and political administrative variables (number of regulations on elderly welfare) were included in the analyses to determine the causal conditions of elderly welfare budget per person. Fs/QCA resulted in three combinations of elderly welfare budget per person: first, the combination of low ratio of elderly people, high ratio of elderly welfare recipients, and low number of regulations on elderly welfare; second, the combination of low ratio of elderly welfare recipients, low financial independence ratio, and high number of regulations on elderly welfare; and lastly, the combination of high ratio of elderly people, high ratio of elderly welfare recipients, and low financial independence ratio. Implications for elderly welfare were made considering socio- economic, financial, and political administrative circumstances based on the study results.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.35-36
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• 2016

Recently, with the increasing demand of high performance of concrete, the mix design of concrete mixture has became low water-to-binder ratio with high binder content. To compensate these trend of mix design, high range water reducer, or superplascizier has been invented to achieve high flowable concrete. Although this superplasticizer provides favorable workability based on its dispersing action on the components of concrete mixture, it has an limitation of decreasing viscosity of the mixture, and thus it is difficult to secure sufficient workability for high performance concrete mixtures with high binder content. To improve the workability of concrete with high viscosity, recently, low-viscosity type superplasticizer was introduced, and in this research, a fundamental properties of low-viscosity type superplasticizer is evaluated.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.240-243
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• 2008

In this paper, the design of Centrifugal Compressor which is used in sizes 50 horse power has 8 pressure ratio and numerical analysis of the flow within compressor varying tip clearance length are performed. To get high pressure ratio with low power the exit height of impellers is low but compressor has very high speed of revolution. So compressor has high specific speed although mass flow rate is very small. The shape of impellers at the first stage is carried out. Flow and performance characteristics of impellers has been analyzed by using a commercial CFD program, $Fine^{TM}$/turbo. The result shows that loss coefficient is affected by tip clearance length and compressor has proper tip clearance length. It is possible to decrease loss by selecting apt tip clearance length.

• Journal of Power System Engineering
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• v.17 no.6
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• pp.115-121
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• 2013

This study was carried out to investigate the effect of hot forging on the hardness and impact value of ultra high carbon low alloy steel. With increasing hot forging ratio, thickness of the network and acicular proeutectoid cementite decreased, and than were broken up into particle shapes, when the forging ratio was 80%, the network and acicular shape of the as-cast state disappeared. Interlamellar spacing and the thickness of eutectoid cementite decreased with increasing forging ratio, and were broken up into particle shapes, which then became spheroidized. With increasing hot forging ratio, hardness, tensile strength, elongation and impact value were not changed up 50%, and then hardness rapidly decreased, while impact value rapidly increased. Hardness and impact value was greatly affected by the disappeared of network and acicular shape of proeutectoid cementite, and became particle shape than thickness reduction of proeutectoid and eutectoid cementite.

• The Journal of Korean Society for School & Community Health Education
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• v.16 no.2
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• pp.17-31
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• 2015

Objectives: This study aimed to analyze the relationship between metabolic syndrome and cataract in a middle-aged men over the age of 40's by using the data from the 5th Korean National Health and Nutrition Examination Survey(2010~2012). Methods: The subjects for the analysis were comprised of 5,808 patients who were at least 40 years or more with metabolic syndrome and cataract. The comparison between the metabolic syndrome and ophthalmic diseases according to the health demographic characteristics, health behavior and health conditions was analyzed with ${\chi}^2-test$. The complex samples logistic regression analysis was used to calculate the odds ratio of cataract according to the health demographic characteristics, health behavior and health conditions and the combination of the comprising factors of the metabolic syndrome. Results: After controlling the confounding factors, the odds ratio of cataract in the metabolic syndrome group was OR 1.30, which was significantly high (p<0.01). Furthermore, the odds ratio of cataract was significantly high in the case of males, as the age increased, educational level decreased, with exercising habits of less than 3 days a week, sun exposure of at least 5 hours, with hypertension and diabetes (p<0.01). The results of analyzing the odds ratio for the occurrence of cataract with the components of metabolic syndrome were OR 1.36 (concurrent high fasting blood glucose, high triglycerides, low HDL cholesterol), OR 1.63 (concurrent high fasting blood glucose, high triglycerides, high waist circumference) and OR 1.33 (high triglycerides, low HDL cholesterol, high waist circumference), which showed significantly high odds ratio for cataract occurrence (p<0.05). Conclusions: We come to know that the relation between metabolic syndrome and components are associate with cataract. Therefore the thorough management of metabolic syndrome and components is needed to prevent cataract.