• Journal of Periodontal and Implant Science
• /
• v.47 no.1
• /
• pp.41-50
• /
• 2017

Purpose: The aims of the present study were to compare the image quality and visibility of tooth cracks between conventional methods and swept-source optical coherence tomography (SS-OCT) and to develop an automatic detection technique for tooth cracks by SS-OCT imaging. Methods: We evaluated SS-OCT with a near-infrared wavelength centered at 1,310 nm over a spectral bandwidth of 100 nm at a rate of 50 kHz as a new diagnostic tool for the detection of tooth cracks. The reliability of the SS-OCT images was verified by comparing the crack lines with those detected using conventional methods. After performing preprocessing of the obtained SS-OCT images to emphasize cracks, an algorithm was developed and verified to detect tooth cracks automatically. Results: The detection capability of SS-OCT was superior or comparable to that of trans-illumination, which did not discriminate among the cracks according to depth. Other conventional methods for the detection of tooth cracks did not sense initial cracks with a width of less than $100{\mu}m$. However, SS-OCT detected cracks of all sizes, ranging from craze lines to split teeth, and the crack lines were automatically detected in images using the Hough transform. Conclusions: We were able to distinguish structural cracks, craze lines, and split lines in tooth cracks using SS-OCT images, and to automatically detect the position of various cracks in the OCT images. Therefore, the detection capability of SS-OCT images provides a useful diagnostic tool for cracked tooth syndrome.

• Polymer(Korea)
• /
• v.31 no.2
• /
• pp.123-129
• /
• 2007

Toughening mechanisms and mechanical properties of three different polyolefin-based composite systems we studied using the tensile, Izod impact and double-notch lout-point-bending (DN-4PB) test, which is well known be an effective tool for probing the failure mechanism (s) around the subcritically propagated crack tip. Microscopy observations such as optical microscopy and transmission electron microscopy were carried out lot the test samples. A detailed investigation clearly shows that a variety of toughening mechanisms, i.e., shear yielding, craze, particle-matrix debonding, rubber particle cavitation, crack deflection and bifurcation, are observed around crack tip damage zone. These toughening mechanisms are responsible for the observed, improved fracture toughness. Based on this study, DN-4PB technique is sufficient to obtain the information needed to describe the fracture behavior of polyolefin-based composites as well as their corresponding toughening mechanisms.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.7 s.262
• /
• pp.732-738
• /
• 2007

Effects of melt-mixing conditions on fracture properties of hydroxyapatite filled bioabsorbable poly(L-lactic acid)(HA/PLLA) composites was investigated by measuring the firacture toughness value of HA/PLLA composites prepared under different mixing time and rotor speed. The fracture surface morphology was also examined by profile measurement and scanning electron microscopies. It was found that the fracture toughness of HA/PLLA composites decreases due to decrease of ductile deformation of PLLA matrix and debonding of interfaces with increase of the rotor speed and mixing time. Effect of mixing process on neat PLLA was also assessed, and it was found that the fracture toughness of PLLA decreases due to disappearance of multiple craze formation and increase of defects. Such thermal and shear-stress degradation were found to be the primary mechanisms of the degradation of HA/PLLA composites during melt-mixing process.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 1992.05a
• /
• pp.121-121
• /
• 1992

Deformation behavior of compatible polymer blends was studied using scanning electron, optical, and transmission electron microscopies. Four different compatible systems were employed and charaterized in this investigation : polystyrene(PS) and polyphenylene oxide(PPO), polystyrene(PS) and polyvinlmethylether(PVME), polystyrene(PS) and poly $\alpha$-methylstyrene(P$\alpha$MS). Individual craze and shear deformation zone microstructures were examined by transmission microscopy (TEM). For TEM observations, specimens deformed in-situ on a TEM grid were utilized. Quantiative analysis of these crazes and shear deformation zones was obtained from the nicrodensitometry of the TEM negatives in the manner developed by Lauterwasser and Kramer. Microdensitometry resulys showed that the fibril extension ratio decreased as the PPO content increased in the PS/PPO blends, and finally, for 100% PPO, only shear deformation zones were observed. For the PS/PVME blends, the ribril extension ratio also decreased as the VME content increased. For the PS/P$\alpha$MS blends, the fibril extension ratio increased as the P$\alpha$MS content increased, For the PPO/P$\alpha$MS blends, the fibril extension ratio increased as the P$\alpha$MS content increased.

• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.1056-1061
• /
• 2003

CD-R disc drive is one of the basic options of personal computer today. In this trend, various CD-R discs can be purchased in every market. Even very low quality discs are in market too. Today's CD-R disc drive is being operated over 10,000 RPM. So the possibility of the disc fracture is growing faster. Sometimes, during the test of a new disc drive by various methods to confirm the quality of it, fracture of the disc happens. And it happens in end user's personal computer scarcely. In this reason, new methods to confirm the quality and the failure mechanism of the optical disc are studied in this paper.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.150-155
• /
• 2004

The base material of optical disc is the amorphous polymer, polycarbonate. So crack growth on the rotating optical disc could happen by the static centrifugal force. This phenomenon is called static fatigue. Today's CD-R disc drive is being operated over 10,000 RPM. This is increasing the possibility of the disc fracture when operating. In this reason, new method to measure the static fatigue threshold quality and the way to calculate the threshold J-integral value and the safe crack length of the optical disc are studied. Finally the environmental effect to optical disc is also studied in this paper.

• Proceedings of the KSR Conference
• /
• 2008.11b
• /
• pp.45-49
• /
• 2008

The monorail system as new transportation system mostly has being constructed as an elevated construction. In particular, in case of construction to elevated structure in the center of a city, it is important to decision for a monorail station to be considered the minimization. We must purchase the required lands prior to design the monorail stations because of separation of a platform and a waiting room. So We can exclude the problem that it have too close between a monorail station and the other building. Therefore the standard width and elevation of the monorail station shall be considered the efficient execution, economic and transportation. We have many thing to resolve as the plan of minimization to the station of monorail. But we know the ultimate in environmentally friendly transportation, of course, is our monorail system and we are positive as to a popular transportation craze.

• Journal of Korea Multimedia Society
• /
• v.24 no.5
• /
• pp.709-716
• /
• 2021

The current trend of entertainment programs is an "Sub-character." This study is to find out which strategies were chosen, considering the entertainment program "Hang Out With Yoo" as the beginning and front-runner of craze for Sub-characters. The following results were deduced: implementation of trendy characters, aggressive acceptance of growth narrative and expansion of episodes. The success or failure of an entertainment program depends on the implementation method of differentiated characters. At this point in time when Sub-characters are continuously developed, this program is meaningful in that it has presented the strategies for Sub-characters reflecting the demand of audience.

• The Journal of Society for e-Business Studies
• /
• v.26 no.3
• /
• pp.155-174
• /
• 2021

This study noted the emergence of the Resell investment within the fashion market, among emerging investment techniques. Worldwide, the market size is growing rapidly, and currently, there is a craze taking place throughout Korea. Therefore, we would like to use shoe data from StockX, the representative site of Resell, to present basic guidelines to consumers and to break down barriers to entry into the Resell market. Moreover, it showed the current status of the Resell craze, which was based on information from various media outlets, and then presented the current status and research model of the Resell market through prior research. Raw data was collected and analyzed using the XGBoost algorithm and the Prophet model. Analysis showed that the factors that affect the Resell market were identified, and the shoes suitable for the Resell market were also identified. Furthermore, historical data on shoes allowed us to predict future prices, thereby predicting future profitability. Through this study, the market will allow unfamiliar consumers to actively participate in the market with the given information. It also provides a variety of vital information regarding Resell investments, thus. forming a fundamental guideline for the market and further contributing to addressing entry barriers.

• Journal of the Korean Society of Fashion and Beauty
• /
• v.3 no.1 s.4
• /
• pp.39-49
• /
• 2005

The purpose of this study is to analyze the consumption value and characteristic of content in cosmetics & perfume advertisement in men's fashion magazines in order to understand the changes of men's cosmetics market which is recently getting great attention along with the craze for 'florally handsome men', and 'eolzzang'(=gorgeous face), and examine the changes of the culture of men's make-up. I selected Esquire which had firstly produced men's fashion magazine in Korea, and implemented the content analysis, the quantitative analysis method, by separating linguistic elements ken visual elements. The results are as follows: In the analysis of consumption value revealed in the linguistic elements of cosmetics advertisement, emotion value was the highest in both cosmetics and perfume, while function value was the second highest in cosmetics and rarity value was the second highest in perfume. About the changes of content characteristics of visual elements, in both cosmetics and perfume advertisement, there were a lot of visual advertisements focused on figures without the mixture of linguistic expressions. Between advertisement in 1990s and that in 2000s, there were meaningful differences only in types and object of meaning of used symbols.