• Journal of Korean Academy of Dental Administration
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• v.9 no.1
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• pp.44-50
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• 2021

Owing to the Corona virus (COVID-19) crisis, virtual education has been expanded. Accordingly, this study was conducted to determine the direction of oral health education by examining participants' satisfaction with virtual education and educational media preferences. This study collected data from a Naver Form online survey targeting 290 university students across the country, from May 10 to 31, 2021. The collected data were analyzed using IBM SPSS 20.0. According to the data, satisfaction with virtual classes was 3.36 points in 5-point Likert scale, satisfaction factors were reduced commuting time and money expenditure, and the highest dissatisfaction factor was a decrease in lecture concentration. The media platform that most interested students pursing oral health education was YouTube. The oral health education that participants wished to receive through virtual education included how to prevent tooth decay, how to prevent gum disease, and how to brush teeth. In conclusion, it is necessary to develop various media like Zoom, YouTube, and virtual reality programs so that students feel motivated to utilize oral health education and improve oral health.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.5
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• pp.24-31
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• 2002

The effects of vortex generators, in the form of small delta-shaped tabs or thin tapes at an axi-symmetric supersonic nozzle exit, on the characteristics of supersonic jet flowfields are investigated by Schlieren images and Pitot-tube measurements. Small tabs as small as 1 % of the nozzle exit area can introduce streamwise vortices and produce a significant effect on the jet flowfield downstream of the nozzle. The effect is stronger for the cases of under-expanded jet than over- and perfect-expanded cases, introducing a larger flow entrainment. The effects of the angle of tabs with respect to the flow direction are also investigated, and for over-expanded jet cases, it is found that the tabs bended toward upstream can weaken the interaction strength and remove the Mach disc in the jet flowfield. Introduction of small proturbances inside the nozzle surface by attachment of thin tapes is also found to change the pressure distribution in the circumferential direction of the flowfield. Its effect is also found to be dependent on the jet expansion ratio.

• Journal of Intelligence and Information Systems
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• v.28 no.1
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• pp.1-28
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• 2022

In recent years, many Internet giants have begun providing their own content services, which attract online users by offering personalized services based on artificial intelligence technologies. This study investigates the role of two firms' content services within the firms' online service network. We examine the role of Naver Webtoon, which can be characterized as a professional-generated content, within Naver's service portfolio, and that of Google YouTube, which can be characterized as a user-generated content, within Google's service portfolio. Using survey data on viewers' use of the two services, we analyze a valued directed service network, where a node denotes an online service and a relationship between two nodes denotes a sequential use of two services. We found that both Webtoon and YouTube show higher out-degree centrality than in-degree centrality, which implies these content services are more likely to be starting services rather than arriving services within the firms' interactive network. The gap between the out-degree and in-degree centrality of YouTube is much smaller than that of Webtoon. The high centrality of YouTube, a user-generated content service, within the Google service network shows that YouTube's initial role of providing specific-content videos (e.g., entertainment) has expanded into a general search service for users.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.279-289
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• 2000

Residual stress induced in U-bending and tube-to-tubesheet joint processes of PWR's row-1 heat exchanger tube was measured by X-ray method and Hole-Drilling Method(HDM). Compressive residual stresses(-) at the extrados surface were induced in U-bending, and its maximum value reached -319 MPa in axial direction at the position of $\psi$ = $0^{\circ}$. Tensile residual stresses(+) of $\sigma_{zz}$ = 45 MPa and $\sigma_{\theta\theta}$ = 25 MPa were introduced in the intrados surface at the position of $\psi$ = $0^{\circ}$. Maximum tensile residual stress of 170 MPa was measured at the flank side at the position of $\psi$ = $90^{\circ}$, i.e., at apex region. It was observed that higher stress gradient was generated at the irregular transition regions (ITR). The trend of residual stress induced by U bending process of the tubes was found to be related with the change of ovality. The residual stress induced by the explosive joint method was found to be lower than that by the mechanical roll method. The gradient of residual stress along the expanded tube was highest at the transition region (TR), and the residual stress in circumferential direction was found to be higher than the residual stress in axial direction.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.04a
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• pp.63-66
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• 2003

Thermoforming of fiber reinforced thermoplastic (FRTP) braided tubes was studied as a new forming technique. FRTP braided tubes with four plies are fabricated by the pressure bonding method are used in thermoforming. Bulge forming, bending process, pipe fittings and FE analysis are carried out in this study. In bulge forming the composite tube can be expanded up to about two times initial diameter. The suggested bending process can be obtained bent products with various bending radii. In pipe fitting it is possible to fabricate T-shape fitting, cross fitting and two-branch fitting. These results exhibit developed forming processes become useful processes for textile composite tubes.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.85.1-85.1
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• 2012

In this study we use three-dimensional magnetohydrodynamic simulations of flux emergence from solar subsurface layer to corona. In order to study the twist parameter of magnetic field we compare the simulations for strongly twisted and weakly twisted cases. Based on the results, we derive a flux expansion factor of selected flux tubes which is a ratio of expanded cross section to the one measured at the footpoint of the flux tube. To understand the effect of flux expansion factor, we make a comparison between magnetic field configuration and the expansion factor. By using a fitting function of hyperbolic tangent we derive noticeable correlations among the strength of the vertical magnetic field, current density and expansion factor. We discuss what these results tell about the relationship between the twist of emerging field and the mechanism for the solar wind.

• Journal of the Korean Chemical Society
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• v.6 no.1
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• pp.54-60
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• 1962

The water gas shift conversion catalyst prepared by the American Cyanamide Co. was subjected to fluidization in a 2-in. Pyrex glass tube to obtain the basic fluidization characteristic data. The size of the catalyst charged ranged from 70 to 120 meshes and it was supported on a single layer 300-mesh wire gauze through which the fluidizing medium, the air, was passed. Following are some data and facts found by the authors: (1) The catalyst particles were porous, and their surfaces were trough and irregular. (2) The average effective particle density and the average shape factor of these particles were 152.2 lb/$ft^3$ and 0.865 respectively. (3) As the particle diameter of the catalyst increased, the minimum fluid voidage of the bed decreased slightly. (4) Just before the incipient fluidization, pressure drop suddenly fell and the bed expanded simultaneously. (5) After fluidization set in, the expansion characteristics of the catalyst bed were similar to those of sand and glass beads except intense bubbling in the catalyst bed.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.09a
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• pp.117-121
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• 1998

The Rapid Expansion of supercritical fluid Solutions (RESS) process was applied to particles coating. Experiments were conducted in a fluidized bed with an internal nozzle in the center of the reaction tube. Microcapsules (mean particle size : 49$\mu\textrm{m}$) prepared by spray drying method were used as the core particles. Supercritical CO2 solutions of paraffin were expanded through the nozzle in to the bed that was fluidized by air. Surface morphology prepared particles was observed by SEM. For the inspection of particle size change, particle size distributions were measured before and after coating. The releasing behavior of Mg2+ ions inspected by AA.

• Journal of Chest Surgery
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• v.22 no.5
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• pp.862-866
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• 1989

We are experienced one case of \ulcornerinchu" method operation for chronic thoracic empyema with bronchopleural fistula. A 30-years old male was admitted to our hospital because of right thoracic empyema. In spite of pleural tube drainage, the right entire lung was poorly expanded. The right upper lobectomy and decortication for visceral side of empyema peel were done but expansion of right middle and lower lobe was not enough to fill the pleural space remained Extraperiosteal detachment without performing thoracoplasty was done as the method proposed by Kinchu. The patient recovered without significant problem and the good expansion of remained lung with acceptable pulmonary function was obtained.ined.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2004.02a
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• pp.17-25
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• 2004

During the past few years, advances have been made in both in X-ray tube and detector technologies. The field of microfocus radioscopy has been established as an important testing process and has expanded into many new industrial applications that require quality control or process optimization. The first nanofocus and multifocus X-ray systems have become available with a focal spot of .5 micron. In the existing range of microfocus X-ray tubes, further improvements have been achieved as well, such as increased long term stability of intensity position constancy. Software, image processing and manipulation techniques have all progressed as well, allowing X-ray to become a formidable non-destructive inspection method for manufacturers in virtually every industry, especially those involved with Electronic Packaging and SMT.