• Journal of the Korean Society for Precision Engineering
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• v.19 no.7
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• pp.36-42
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• 2002

This paper presents two actuators for levitation using repulsions of permanent magnet and two magnetic levitation tables using the actuators. Here, one actuator for levitation consists of one fixed magnet and one moving magnet, and the other actuator consists of two fixed magnets and one moving magnet. The moving part of the magnetic levitation table contains the moving magnets. repulsive forces caused by the permanent magnets are linearized, and then the equation of motion of the moving part of the table is derived. Using the equation of motion, stability conditions of the moving part are deduced. The stability conditions are analyzed for positional relations of the moving magnets and the minimum number of active control required for stable system. As a result, in the each case of magnetic levitation tables, the requirements for stabilization are expressed by the positional relations and the number of the active controls.

• The Journal of Engineering Geology
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• v.3 no.1
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• pp.39-49
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• 1993

Intrinsic random function of order k(IRF-k) was used to estimate groundwater levels of nonstationaav random functions. The accuracy of IRF-k was compared to that of ordraarv krigrng assuming that the data of groundwater levels compose a stafionarv random function. Cross validation and statistical errors show that IRF-k is superior to orcinarv '(riging for the estimation of water levels. IRF-k and ordinary kriging made different contour and 3-D surface maps. The maps of IRF-k are more accurate than those of ordinary kriging.

• Analytical Science and Technology
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• v.17 no.6
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• pp.520-526
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• 2004

To determine 6 anti-impotence drug-like compounds such as sildenafil, vardenafil, tadalafil, homosildenafil, hydroxyhomosildenafil and hongdenafil in food, simultaneously, high performance liquid chromatography was applied. In the case of solid sample, it was extracted in organic solvents after homogenizing with mortar and pestle. Whereas liquid sample was just diluted in water and then extracted in organic solvents. Maximum lengths of UV for targets have been identified on photodiode array spectra. As results, vardenafil, hongdenafil, hydroxyhomosildenafil, sildenafil, homosildenafil, and tadalafil were eluted in order using $C_{18}$ column in acetonitrile containing phosphoric acid as the mobile phase. The maximum wavelength (${\lambda}_{max}$) was 216 nm for vardenafil, 233 and 282 nm for hongdenafil, 222 and 293 nm for hydroxyhomosildenafil, sildenafil and homosildenafil, and 284 nm for tadalafil. The overall recoveries were ranged from 95% to 109% and the limit of detection was about 0.04 mg/kg at signal/noise>3. Levels of targets in the selected food samples were 1.7 (hongdenafil) ~ 63 (tadalafil) mg/one dose.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.7
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• pp.125-132
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• 2002

This paper shows an experimental magnetic levitation table using one degree-of-freedom active control. The magnetic levitation table using repulsions of permanent magnets was theoretically presented already. Thus the objective of this paper is to prove stable levitation with only one degree-of-freedom active control experimentally. For the design of the system, at first, permanent magnets are selected. Secondly, the spring constants of the virtual spring are obtained by simulation. Thirdly, the moving magnets are arranged using a stable layout relation. Fourthly, a linear voice coil motor is designed. Finally, the magnetic levitation system is manufactured. The phenomenon of stable levitation in the manufactured table is proven by means of dynamic time and frequency responses. The differences between the theoretical natural frequencies and experimental ones are analyzed. Also, stable range in the control direction is shown experimentally.

• Journal of Digital Convergence
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• v.18 no.4
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• pp.101-112
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• 2020

This study aims to discuss the current status of the ride-sharing platform industry, which embodies the core values of the 4th Industrial Revolution, sharing and connectivity, as well as economic, industrial, and legal issues. To understand the position of competing groups, the research conducted extensive literature reviews on domestic and international cases of technical and legal issues of the sharing economy. The result indicates that the ride sharing industry showed the economy of synthesis in which production, supply, distribution, and consumption are on one platform. It made possible to share values to users and synthesize them with new services through easy-access mobile application technology. To resolve the conflicts between the taxi industry and the ride sharing industry, this study suggests the following: Ride-sharing companies should make contributions to provide legitimate services. The taxi industry needs to understand the value of the new industry and consumers who chose the shared platform service. The significance of the current study is that it proposed a comprehensive analysis and policy direction toward the issue of balance between public and private interests and legal stability.

• Journal of the Korean Society of Food Science and Nutrition
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• v.12 no.4
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• pp.387-394
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• 1983

The factor, which was capable of accelerating the yeast cell wall lysis of the zymolyase(${\beta}-1$, 3-glucanase), was purified to a homogeneous state from the protease fraction of the crude zymolyase by Sephadex G-75 gel filtration and preparative polyacrylamide gel disc electrophoresis. The molecular weight of the purified factor was estimated to be 40,500 by SDS-polylacrylamide gel disc electrophoresis and it's iso-electric point was pH 9.6. The factor was found to be a basic protease consisted of single polypeptide chain with 395 amino acid residues and it showed the $E_{280,cm}^{1%}$ of 11.9 and the molecular extinction coefficient of $4.83{\times}10^4$, respectively.

• Journal of Digital Convergence
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• v.17 no.7
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• pp.351-357
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• 2019

A number of case studies and type analyzes have been conducted on mobility platform services that are rapidly evolving around the world. However, since the actual user experience is important for the development of the mobility service, research on the user side is needed. In the mobility platform service, only the car-hailing was used, and the preference factors were analyzed through the questionnaire in seven aspects of the user experience. Studies have shown significant differences according to gender. While the safety of the woman, the comfort and the kindness of the vehicle have a great influence on the satisfaction, the male affirms that the familiarity is the factor affecting the satisfaction. This study focused on the customer experience as a real user and identified key factors of selecting mobility platform service, so it is expected that it will contribute to the development of mobility platform service in the future.

• Analytical Science and Technology
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• v.20 no.1
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• pp.78-83
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• 2007

To perform proficiency test for determining anti-impotence drug-like compounds in food, interlaboratory test has been done. Targets were 6 such as sildenafil, tadalafil, vardenafil, homosildenafil, hydroxy-homosildenafil and pseudo-vardenafilI. Total 13 institutes were participated and all is in charging of food analysis. To do double blind test, the reference materials were made as 13 different ginseng drink samples and each sample had random 3 targets. By the official method for anti-impotence drug-like compounds in food code, sample was just diluted in water, extracted in organic solvents, determined by HPLC/UV and then confirmed by LC/MS. The analytical duration was 60 days after receiving sample. Ten out of 13 institutes were satisfied by evaluation of Z-score and RSZ according to the regulation for managing analytical quality assurance.

• Journal of the Korean Geographical Society
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• v.51 no.3
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• pp.327-344
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• 2016

We may have an incorrect view of Korea and the world by misunderstanding them with a number of geographic misconceptions. Such misconceptions constructed socially tend to perpetuate through reproducing and learning repeatedly from one generation to the next. 'Daegu city is in the intermontane basin.' It is also identified that this geographic misconception had constructed (made) by two Japanese geographers (Tamura, 1933; Tada, 1940) in the Japanese colonial period, and have been reproduced and diffused by many Korean geographers (professors and teachers) as well as journalists in the post-colonial days. In terms of the definition of an intermontane basin in the Encyclopedia of Geomorphology published by the International Association of Geomorphologists, Daegu seems not to be a basin city but to be a plain city, since the central plain of Daegu is surrounded by higher terrain like mountains and hills only on the north and south directions of all sides, and also it is well developed thanks to its location where the downstream of the Geumhogang river flows from east to west. This paper hopes that the landform recognition as 'Daegu intermontane basin city' should be corrected as soon as possible, and also many geographic misconceptions will be studied actively for an accurate understanding of Korea and the world.

• Analytical Science and Technology
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• v.16 no.1
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• pp.32-38
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• 2003

The rapid and sensitive determination method of sildenafil and its related compounds (Vardenafil, Homosildenafil, Tadanafil.) has been investigated using high performance thin layer choromatography (HPTLC). Optimizing separation conditions and simultaneous determination method of these compounds were studied. The calibration curves of those compounds at 254 nm was found to be linear in the range of $1.0{\sim}56.5{\mu}g/mL$, respectively. The detection limts (LOD) and quantification limits (LOQ) of these were found to be $0.8{\sim}1.8{\mu}g/mL$ and $1.0{\sim}2.3{\mu}g/mL$. The coefficient of variation (C.V.) were less than 2.5%. Finally, the present method was applied to determine sildenafil and its related substances in dietary supplement.