• Journal of Technologic Dentistry
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• v.42 no.3
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• pp.228-233
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• 2020

Purpose: This study aimed to assess and compare the marginal fit of ceramic-based hybrid resin restoration (HYB) and zirconia restoration (ZIR) for dental computer-aided design/computer-aided manufacturing systems. Methods: A stainless steel master model was produced. The impression was first made with silicone, and then stone working models were produced. A total of twenty restorations were fabricated with two different materials: ZIR and HYB. The silicone film thickness of the marginal gap was measured using a digital microscope; digital photos were taken at a magnification of ×160, and then analyzed using a measurement software. The values of the result were evaluated with the independent-sample t-test (α=0.05). All statistical analyses were performed with a statistical software. Results: The mean values for the marginal gap was 37.14±2.96 ㎛ for HYB, compared with 40.37±5.26 ㎛ for ZIR. No significant difference was found between ZIR and HYB (p=0.107). Conclusion: As a result, the marginal fit of the restoration fabricated using the hybrid resin was better than that of the restoration fabricated using zirconia. Also, the marginal fit of all groups was below the clinical acceptable range of 120 ㎛. Thus, HYB for dental CAD/CAM system in this study is expected to be suitable for clinical use in dentistry.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.25 no.2
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• pp.281-286
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• 1995

Tooth length determination is a crucial step in endodontic treatment. Traditionally, radiographs are used to confirm working length of the root length. This study was performed to evaluate the radiographic distortion(magnification) and calculate correction coefficients for the object-film distance. Ninty-six radiographs were made of eight extracted teeth(two upper first premolars, two lower first premolars, two upper first molars, and two lower first molars) by using the 16 inch long cone paralelling techniques with 1mm interval from 5 to 16mm tooth-film distance. The results were as follows. 1. The least mean radiographic distortion from 5 to 16mm tooth-film distance was 2.42±0.68％(the length of mesiobuccal cusp-mesial root of lower first molars), the greatest distortion was 4.74±1.36％(the length of mesiobuccal cusp-mesiobuccal root of upper first molars). 2. The greatest correction coefficient was 0.986(the mesiobuccal cusp-mesial root of lower first molars, the lowest one was 0.937(the mesiobuccal cusp-mesiobuccal root of upper first molars).

• The Journal of Korean Academy of Prosthodontics
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• v.24 no.1
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• pp.151-164
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• 1986

The purpose of this study was to evaluate the marginal fit of metal ceramic crowns made by different techniques. The techniques were metal butt margin technique, platinum foil technique, shoulder powder techniques and wax technique. The latter three techniques were for the fabrication of collarless metal ceramic crowns. Ten crowns were made of each techniques, and marginal fit was evaluated using scanning electron microscope under X200 magnification. The results were as follows. 1. The marginal fit in the descending order were wax technique shoulder powder technique, platinum foil technique and metal butt margin, before cementation, and wax technique, shoulder powder technique, metal butt margin, and platinum foil technique, after cementation. 2. The fit of collarless metal ceramic crowns was comparable to metal ceramic crowns with metal butt margins. 3. There were no statistically significant differences between marginal fit of metal ceramic crowns made by different techniques.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.471-472
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• 2007

The scalp is skin tissue for skull-protection and roots for hair growth. Therefore continuous monitoring of scalp condition is essential for hair management. However, the equipments for existent are inconvenient to use because of focus tremor and external factors(Hair Gel, Wax, accessories and so on). Furthermore there is a problem to use an expensive optical devices like CCD (Charge Coupled Device) camera or lens of 200 - 1000 magnification. It causes a difficulty of using those equipment. We design the special electrode(length 5.65mm, diameter 0.8mm of needle shape) and the impedance system(1kHz, 78uA). Tn this paper, we can measure scalp impedance with our system. Moreover, we find the possibility of classifying scalp condition with measured impedance values. For the classification of scalp condition, we used ARAMO-TS as an imaging system. In conclusion, the problem of existent devices could be improved using these method. It also has a benefit of continuous monitoring of scalp condition.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.908-910
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• 1998

Modern AC electric car has PWM(Pulse Width Modulation) -controlled converters, which give rise to higher harmonics. The current harmonics injected from AC electric car is propagated through power feeding circuit. As the feeding circuit is a distributed constant circuit composed of RLC, the capacitance of the feeding circuit and the inductance on the side of power system cause a parallel resonance and a magnification of current harmonics at a specific frequency. The magnified current harmonics usually brings about various problems. That is, the current harmonics makes interference in the adjacent lines of communications and the railway signalling system. Furthermore, in case it flows on the side of power system, not only overheating and vibration at the power capacitors but also wrong operation at the protective devices can occur. Therefore, the exact assessment of the harmonic current flow must be undertaken at design and planning stage for the electric traction systems. From these point of view, this study presents an approach to model and to analyse traction power feeding system focused on the amplification of harmonic current. The proposed algorithm is applied to a standard AT(Auto-transformer)-fed test system in which electric car with PWM-controlled converters is running.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.12
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• pp.1056-1061
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• 2007

A sublimation epitaxial method, referred to as the Closed Space Technique (CST) was adopted to produce thick SiC epitaxial layers for power device applications. In this study, we aimed to systematically investigate surface morphologies and electrical properties of SiC epitaxial layers grown with varying a SiC/Al ratio in a SiC source powder during the sublimation growth using the CST method. The surface morphology was dramatically changed with varying the SiC/Al ratio. When the SiC/Al ratio of 90/1 was used, the step bunching was not observed in this magnification and the ratio of SiC/Al is an optimized range to grow of p-type SiC epitaxial layer. It was confirmed that the acceptor concentration of epitaxial layer was continuously decreased with increasing the SiC/Al ratio. 4H-SiC MESFETs haying a micron-gate length were fabricated using a lithography process and their current-voltage performances were characterized. It was confirmed that the increase of the negative voltage applied on the gate reduced the drain current, showing normal operation of FET device.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.4
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• pp.562-569
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• 2010

This paper analyzes the problems that occurred in the magnification process for a fine input image and investigates a method to improve the blurring of magnified image. This paper applies a curve interpolation algorithm in CAD/CAM for the same test images with the existing image algorithm in order to improve the blurring of magnified image. As a result, the nearest neighbor interpolation, which is the most frequently applied algorithm for the existing image interpolation algorithm, shows that the identification of a magnified image is not possible. Therefore, this study examines an interpolation of gray-level data by applying a low-pass spatial filter and verifies that a bilinear interpolation presents a lack of property that accentuates the boundary of the image where the image is largely changed. The periodic B-spline interpolation algorithm used for curve interpolation in CAD/CAM can remove the blurring but shows a problem of obscuration, and the Ferguson' curve interpolation algorithm shows a more sharpened image than that of the periodic B-spline algorithm. For the future study, hereafter, this study will develop an interpolation algorithm that has an excellent improvement for the boundary of the image and continuous and flexible property by using the NURBS, Ferguson' complex surface, and Bezier surface used in CAD/CAM engineering based on the results of this study.

• Journal of the Korea Society of Computer and Information
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• v.18 no.2
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• pp.49-57
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• 2013

To improve the quality of magnified image, two schemes were proposed. The one is used to estimate simple convex surface and simple concave surface using the information of adjacent pixel values, and the other scheme is used to produce magnified image using the characteristics of simple convex surface and simple concave surface. The magnified image using the proposed scheme is more similar to real image than the magnified image using the previous schemes. The PSNR values of the magnified images using the proposed scheme are greater than those of the magnified images using the previous interpolation schemes.

• ETRI Journal
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• v.33 no.2
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• pp.251-258
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• 2011

Applying face alignment after face detection exerts a heavy influence on face recognition. Many researchers have recently investigated face alignment using databases collected from images taken at close distances and with low magnification. However, in the cases of home-service robots, captured images generally are of low resolution and low quality. Therefore, previous face alignment research, such as eye detection, is not appropriate for robot environments. The main purpose of this paper is to provide a new and effective approach in the alignment of small and blurred faces. We propose a face alignment method using the confidence value of Real-AdaBoost with a modified census transform feature. We also evaluate the face recognition system to compare the proposed face alignment module with those of other systems. Experimental results show that the proposed method has a high recognition rate, higher than face alignment methods using a manually-marked eye position.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.6
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• pp.9-16
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• 2008

Recently, there are a lot of multimedia products using image interpolation system. However, most interpolation systems in existence suffer visually to some extents from the effects of blurred edges and jagged artifacts in the image. In this paper, we propose a new adaptive linear interpolation system that uses the sub-pixel. The proposed system calculate the warped distance among the pixels of an image by optimizing length parameter. A new cost function is introduced to reflect frequency properties of the origin data in order to improve image quality. Experimental results show that our new algorithm significantly outperforms conventional interpolation methods in subjective quality, and in most cases, in terms of PSNR as well.