• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.3
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• pp.311-319
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• 1999

The thermal conductivity ${\lambda}_b$, thermal diffusivity ${\alpha}_b$ of the thin black paint layer sprayed on solid surface and absorptivity a for laser beam are measured by applying a non-contact measurement method of the thermophysical properties of solids. The values of a=0.67, ${\lambda}_b=1.45W/mK$ and ${\alpha}_b=1.24{\times}10^{-6}m^2/s$ are obtained for the sprayed lay~ thickness $z_b{\fallingdotseq}40\;{\mu}m$. Furthermore, for the $z_b{\fallingdotseq}24\;{\mu}m$ thick layers which arc formed by rubbing with a glass rod after spraying, the values of a=0.73, ${\lambda}_b=1.85W/mK$. and ${\alpha}_b=1.09{\times}10^{-6}m^2/s$ are obtained. It is also shown that the present thermal diffusivity ${\alpha}_b$ for $z_b{\fallingdotseq}40\;{\mu}m$ Is about 30~80% larger than those obtained by Araki et al. for the thicker layer $z_b{\fallingdotseq}150{\sim}248\;{\mu}m$. This method could be applied to the measurement of thermophysical properties of thin layer on solids.

• Journal of computational fluids engineering
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• v.6 no.1
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• pp.21-30
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• 2001

A numerical study on the similarity of the developing laminar flows between in a straight duct rotating about an axis perpendicular to that of the duct and in a stationary curved duct was carried out. In order to clarify the analogy of two flows, dimensionless parameters K/sub LR/ = Re/(equation omitted) and Rossby number, Ro, in a rotating straight duct were used as a set corresponding to Dean number K/sub LC/ = Re/(equation omitted), and curvature ratio, λ, in a stationary curved duct. For the large values of Ro and λ, it is shown that the flow field satisfies the 'asymptotic invariance property', that is, there are strong quantitative similarities between the two flows such as flow patterns, friction factors, and maximum axial velocity magnitudes for the same values of K/sub LR/ and K/sub LC/ if they are correlated with dimensionless axial distances Z/sub R/ = z/(equation omitted) for a rotating duct flow and Z/sub C/ = z/(equation omitted) for a stationary curved duct flow.

• Journal of Biomedical Engineering Research
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• v.17 no.2
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• pp.165-172
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• 1996

A scanning slot digital mammography system Luing a plastic scintillating fiber screen (SFS) is currently being developed To improve the x-ray interaction efficiency and absorption efficiency of an SFS, high Z elements can be added into the scintillating fiber core. In this paper, we investigated theoretically the zero spatial frequency detective quantum efficiency, DQE(0), and modulation transfer function, MTF(f), of three 2 cm thick SFSs made of polystyrene, polystyrene loaded with 5% by weight of lead, and polystyrene Loaded with 10% by weight of tin scintillating fibers. X-ray interaction efficiency, scintillating light intensity distributions and line spread functions were generated using Monte Carlo simulation. DQE(0) and MTF(f) were computed for x-ray energies ranging from 15 to 50 keV. Loading high Z elements into the SFS markedly increased the DQE(0). For x-ray energies used for mammovaphy, DQE(0) values of both high Z element loaded SFSs are about a factor of three higher than the DQE(0) of an Min-R screen. At mammographic x-ray energies, MTF(f) values of all three SFSs are Venter than 50% at 25 Ip/mm spatial frequency, and were found to be dominated by the 20 um individual scintillating fiber diameter used The results show that both hiP DQE(0) and spatial resolution can be achieved with the high Z element loaded SFSs, which make these SFSs attractive for use in a scanning slot detector for digital mammography.

• Journal of Astronomy and Space Sciences
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• v.28 no.2
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• pp.123-132
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• 2011

It is generally believed that the occurrence of a magnetic storm depends upon the solar wind conditions, particularly the southward interplanetary magnetic field (IMF) component. To understand the relationship between solar wind parameters and magnetic storms, variations in magnetic field polarity and solar wind parameters during magnetic storms are examined. A total of 156 storms during the period of 1997~2003 are used. According to the interplanetary driver, magnetic storms are divided into three types, which are coronal mass ejection (CME)-driven storms, co-rotating interaction region (CIR)-driven storms, and complicated type storms. Complicated types were not included in this study. For this purpose, the manner in which the direction change of IMF $B_y$ and $B_z$ components (in geocentric solar magnetospheric coordinate system coordinate) during the main phase is related with the development of the storm is examined. The time-integrated solar wind parameters are compared with the time-integrated disturbance storm time (Dst) index during the main phase of each magnetic storm. The time lag with the storm size is also investigated. Some results are worth noting: CME-driven storms, under steady conditions of $B_z$ < 0, represent more than half of the storms in number. That is, it is found that the average number of storms for negative sign of IMF $B_z$ (T1~T4) is high, at 56.4%, 53.0%, and 63.7% in each storm category, respectively. However, for the CIR-driven storms, the percentage of moderate storms is only 29.2%, while the number of intense storms is more than half (60.0%) under the $B_z$ < 0 condition. It is found that the correlation is highest between the time-integrated IMF $B_z$ and the time-integrated Dst index for the CME-driven storms. On the other hand, for the CIR-driven storms, a high correlation is found, with the correlation coefficient being 0.93, between time-integrated Dst index and time-integrated solar wind speed, while a low correlation, 0.51, is found between timeintegrated $B_z$ and time-integrated Dst index. The relationship between storm size and time lag in terms of hours from $B_z$ minimum to Dst minimum values is investigated. For the CME-driven storms, time lag of 26% of moderate storms is one hour, whereas time lag of 33% of moderate storms is two hours for the CIR-driven storms. The average values of solar wind parameters for the CME and CIR-driven storms are also examined. The average values of ${\mid}Dst_{min}{\mid}$ and ${\mid}B_{zmin}{\mid}$ for the CME-driven storms are higher than those of CIR-driven storms, while the average value of temperature is lower.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.4
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• pp.353-361
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• 2019

The aim of this study was to evaluate the color stability of bulk-fill and conventional resin composites with respect to different storage media and thickness of composites. Filtek™ Z250 and Filtek™ Z350XT were evaluated as conventional resin composites. Filtek™ Bulk-fill Posterior Restorative and Tetric^® N-Ceram Bulk Fill were evaluated as bulk-fill resin composites. CIE L^*a^*b^* values of baseline were measured after 24 hours of storage in distilled water, and each resin composite group was divided into three subgroups and stored in distilled water, red wine, and coffee media respectively. Again after 1, 7 and 28 days of immersion, color changes (ΔE^*) were calculated using the CIE L^*a^*b^* values. The greatest ΔE^* was observed in red wine for all resin composites, and the mean color changes were ranked in the increasing order of distilled water, coffee, red wine. Filtek™ Z350XT exhibited the greatest color change in all media, followed by Filtek™ Bulk-fill Posterior Restorative. Filtek™ Z250 and Tetric^® N-Ceram Bulk Fill followed with similar mean color change values. According to the 2 different thicknesses of 2 mm and 4 mm of bulk-fill resin composites, there was no thickness-related difference on color changes.

• Human Ecology Research
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• v.60 no.3
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• pp.377-390
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• 2022

This study identified and compared family values within and across different generations concerning gender roles, attitudes toward diverse families, children, and parental roles. Data were obtained from the 2020 Seoul Family Report Survey. There were 1,949 study subjects, including first- and second-generation baby boomers and individuals in generations X, Y, and Z in Korea. Latent profile analyses were conducted using M-plus. Perceptions and views concerning family values were classified into different types. The main findings were as follows. Two types were identified among first baby boomers, and three were identified among second baby boomers. Most of the first and second baby boomers belonged to the "moderate" type. Two types were detected among those in Generation X. Regarding gender roles, most views of Generation X were slightly progressive, while their other family values were more moderate. Three types were identified among those in Generation Y: "progressive," "moderate," and "very liberal." Generation Z was identified as a "progressive" group. This study provides basic data to explore the direction of the coexistence of generations by identifying and comparing diverse family values within and across generations.

• Industry Promotion Research
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• v.9 no.3
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• pp.129-138
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• 2024

This study investigates the impact of Generation Z's consumer characteristics on the E-commerce industry using data from 60 respondents through an online survey. Generation Z, accustomed to the digital environment and quickly adopting new technologies, is noted as a strong consumer group. The study results indicate that value-driven and digital-friendly consumption significantly impact E-commerce usage. This suggests that E-commerce companies should enhance the digital experience and emphasize social responsibility and ethical values in their marketing strategies. These findings provide foundational data for effectively analyzing and responding to Generation Z's consumer characteristics in the E-commerce market.

• Journal of Korea Multimedia Society
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• v.8 no.2
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• pp.249-257
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• 2005

This paper aims at reducing aliasing in pixel-based rendering for 3D implicit surfaces by shifted multi Z-buffers. The voxelized implicit surfaces with high resolution take so much time in generating high Quality image without aliasing. So in rendering a voxelized implicit surfaces, a new antialiasing method which can generate a high quality image at a lower resolution is required. Therefore, this paper suggests that a method which get various sampling values by shifting several z-buffers in each voxel and average them, The advantages are effective memory, simple calculation and easy convergence with various filters. But, the increase of number of z-buffer also increase the consuming time rapidly. Therefore, the research for representing the relation the degree of image quality with the consumption of time as a number is required.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.2
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• pp.1043-1053
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• 2021

The purpose of this research is to investigate the impacts of gen-Z's perception of consumer-generated content on social media on their travel intention with the mediating role of travel motivation push and pull. An online questionnaire survey of a total of 369 samples was conducted with the participation of gen Z in the most important cities across Vietnam. The model was analyzed using Structural Equation Modeling (SEM) using AMOS program 22 to investigate model relationships and all hypotheses are significant. The findings indicated that gen Z values the usefulness of social media and they use social media for knowledge-seeking (push factor), and this leads to their intention to visit a destination. SEM analysis also reveals that gen Z tends to use social media to find accessibility to any destinations and they are motivated highly with destinations that have clear and easy access, for example, no visa requirement or neighboring destinations. As the result, they have better intentions to visit these destinations. This research will help marketers, especially marketing specialists to gain a better understanding of gen Z, thus implement better marketing techniques to target gen Z.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.389-392
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• 2000

Gouge-free tool-path generation is an important issue in mold & die machining and researches on cutter interference avoidance can be found in many articles. One of the various methods is construction of tool-offlet surface or cutter-location (CL) surface on which the cutter-center point (CL-point) locates. Provided that the CL surface is represented in a suitable form, cutter-interference avoidance can be performed without the burden of computing CL data for every cutter-contact (CC) point. In the paper, various methods of constructing a CL surface in the z-map form are presented, where z-map is a special form of discrete nonparametric representation in which the height values at grid points on the xy-plane are stored as a 2D array z［i,j］.