• Restorative Dentistry and Endodontics
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• v.10 no.1
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• pp.103-114
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• 1984

The purpose of this study was to compare the polished surfaces of two composite resins (Clearfil F and Durafill) with those of glass ionomer cement (Fuji ionomer cement) and to observe what types of polishing devices are valuable, and then to establish a clinically satisfactory procedures. Studies have been undertaken to determine the effects of glass plate matrix and finishing instruments (Carborundum point, White point and Sof-Lex medium) on the surface finish of three restorative materials. The results were examined with profilometer (Kosaka laboratory LTD. Tokyo, Japan) and scanning electron microscopy (JSM-T20: JEOL). The results were as follows: 1. The most satisfactory surface finishes were produced against glass matrix. 2. Coarser finishes were obtained with use of carborundum point. 3. Generally Fuji ionomer cement were left surfaces with higher roughness values. 4. The smoothest finishes were obtained with Sof-lex medium. 5. Clearfil-F was showed more smoother than the other restorative materials.

• Korean Journal of Computational Design and Engineering
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• v.14 no.1
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• pp.18-24
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• 2009

This paper proposes an analytical method of evaluating the maximum error by modeling the exact tool path for the tool traverse singular region in five-axis machining. It is known that the NC data from the inverse kinematics transformation of 5-axis machining can generate singular positions where incoherent movements of the rotary axes can appear. These lead to unexpected errors and abrupt operations, resulting in scoring on the machined surface. To resolve this problem, previous methods have calculated several tool positions during a singular operation, using inverse kinematics equations to predict tool trajectory and approximate the maximum error. This type of numerical approach, configuring the tool trajectory, requires much computation time to obtain a sufficient number of tool positions in a region. We have derived an analytical equation for the tool trajectory in a singular area by modeling the tool operation into a linear and a nonlinear part that is a general form of the tool trajectory in the singular area and that is suitable for all types of five-axis machine tools. In addition, we have evaluated the maximum tool-path error exactly, using our analytical model. Our algorithm can be used to modify NC data, making the operation smoother and bringing any errors to within tolerance.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.23 no.2
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• pp.335-344
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• 1993

The purpose of this study was to clarify the spatial relationship of temporomandibular joint and to an aid in the diagnosis of temporomandibular disorder. For this study, three-dimensional images of normal temporomandibular joints were reconstructed by computer image analysis system and three-dimensional reconstructive program integrated in computed tomography. The obtained results were as follows: 1. Two-dimensional computed tomograms had the better resolution than three dimensional computed tomograms in the evaluation of bone structure and the disk of TMJ. 2. Direct sagittal computed tomograms and coronal computed tomograms had the better resolution in the evaluation of the disk of TMJ. 3. The positional relationship of the disk could be visualized, but the configuration of the disk could not be clearly visualized on three-dimensional reconstructive CT images. 4. Three-dimensional reconstructive CT images had the smoother margin than three-dimensional images reconstructed by computer image analysis system, but the images of the latter had the better perspective. 5. Three-dimensional reconstructive images had the better spatial relationship of the TMJ articulation, and the joint spaces were more clearly visualized on dissection images.

• Journal of the Korean GEO-environmental Society
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• v.18 no.11
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• pp.19-26
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• 2017

When narrowly excavated in the urban area, the wall of backfill space is not only symmetrical but also asymmetrical. In this case, the horizontal stress induced by backfilling depends mostly on the wall asymmetry and the wall friction angle. Therefore, in this study, the model test in the laboratory was conducted to investigate horizontal earth pressure with depth considering various boundary conditions such as base width, wall friction, relative density of backfill, and wall angle. As the wall is smoother and wall angle is lower from the bottom, the results showed higher the horizontal stresses due to the increase of vertical stresses.

• Journal of the Korean Ceramic Society
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• v.20 no.4
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• pp.289-296
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• 1983

The Wetting of fusion cast $Al_2O_3$ brick and $Al_2O_3 -ZrO_2$ brick by liquid Ag was studied by the sessile drop technique in Ar atmosphere. In this experiment the specimens were photographed per 2$0^{\circ}C$with increasing temperature from 96$0^{\circ}C$ melting point of Ag. And the method of photographing was carried out by shadow technique. The cosine of the contact angle increased linearly with increasing temperature in both systems. And the relation between the cosine of the contact angle and the temperature was Cos$\theta$=1.132+$0.75{\times}10^{-3}T$ for $Al_2O_3$ brick and Cos$\theta$=-1.706+$1.125{\times}10^{-3}T$ for $Al_2O_3 -ZrO_2$ brick In both systems the contact angle decreased as the surface of substrate became smoother. The work of adhesion which was 503.5ergs/$cm^2$ for $Al_2O_3$brick and 393.6 ergs/cm2 for $Al_2O_3 -ZrO_2$ brick at 96$0^{\circ}C$ increased parabolically with increasing temperature in both system.

• Progress in Superconductivity and Cryogenics
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• v.13 no.4
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• pp.18-21
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• 2011

In this work, the yttrium oxide($Y_2O_3$) thin films as the buffer layer were prepared by the simple solution coating and reel-to-reel process on an unpolished metal tape substrate. The $Y_2O_3$ thin films were successfully synthesized by the hydrolysis of yttrium acetate. We have studied the improvement of surface roughness with the concentration of solution(0.1 M, 0.4 M, M) and the number of coatings. The planarization by solution coating process is simple in comparison with the existing polishing process, and it is eco-friendly, and has the benefits of low cost process. The thickness of $Y_2O_3$ films was increased with the $Y_2O_3$ concentration in the solution, and the surface became smoother with the number of coating cycles. Using this process, we have achieved 1.2 nm RMS roughness from a starting roughness of over 31 nm on 25 ${\mu}m^2$ area.

• Korean Journal of Agricultural Science
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• v.44 no.1
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• pp.23-29
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• 2017

This study was conducted to explore which pollen type could be an effective pollen source for self-incompatible 'Niitaka' pear (Pyrus pyrifolia Nakai), when different pollinizers were to be applied. The pollens of five different pears with similar flowering times were applied to bagged 'Niitaka' flowers grown in Cheonan city, Korea. Pollen types used were of different origins including Korean pears ('Wonhwang' and 'Chuhwangbae'), Japanese pears ('Chojuuro' and 'Okusankichi'), and Chinese pear ('Yali'). Results show that the amount of pollen produced by flowers of each cultivar was the largest in Korean pear 'Wonhwang' (234 g/100 flowers) and the smallest in Japanese pear 'Okusankichi' (126 g/100 flowers). A high proportion of large fruits (> 600 g), 71.4% of total production, was found in the fruits treated with 'Yali' pollen. However, these fruits showed an unfavorable external appearance. Based on individual fruit width differences, 'Chojuuro' treatment produced the smallest difference in fruit diameters (3.2 mm) and 'Yali' treatment' gave the largest (4.8 mm). Also, the difference in fruit length was the largest in 'Yali' (7.5 mm), which also produced the most uneven fruits among the pollinizers used. Meanwhile, the use of pollens of 'Wonhwang' and 'Chuhwangbae' improved productivity by increasing the fruit shape index and the ratio of bigger fruits in total production. Moreover, those pollens also decreased the development of lenticels on fruit skins which gave them a smoother appearance.

• Corrosion Science and Technology
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• v.8 no.6
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• pp.209-216
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• 2009

In this study the effect of different surface finishing techniques on the pitting corrosion behaviour of a commercial 304 stainless steel alloy was investigated. Surface finishing methods were divided into two categories, i.e. mechanical and chemical. Mechanical treatment methods include power tooling such as grinding, emery paper brushing, stainless steel wire brushing and stainless steel shot blasting. Chemical treatment methods include chemical passivation (phosphoric acid, citric acid, nitric acid) and electro-cleaning (phosphoric acid and citric acid). Potentiodynamic polarization experiments were carried out in 3.5 wt. % NaCl solution at room temp. (20 $^{\circ}C$). The results showed that chemical treatment methods improved the corrosion resistance of stainless steel 304, measured in terms of pitting potential ($E_{pit}$). Corrosion resistance of the specimens was increased in the order of; electro-cleaning > manual passivation > mechanical cleaning. Surface of electro-cleaned specimens was smoother than rest of the surface treatment methods. Chrome content in chemically treated specimens was higher than in mechanically treated specimens as shown by EDX analysis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.5
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• pp.220-230
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• 2017

In this study we apply and compare a variety of numerical methods for calculating residence time distribution in decay tanks, a major design component in the for reducing N-16 radioactivity. Our research group has used a streamlined method using user-defined particle numbers. However, this streamlined method has several problems, including low exiting particle ratios, particle diminishing, and unphysical time distribution, among others. We utilize three numerical methods to establish residence time and time distribution (streamlined, discrete phase method [DPM], and user defined scalar [UDS]) and subsequently compare the averaged results of each. The three tests demonstrate the flow features within the decay tanks, which are then numerically simulated to enable comparison. We conclude that although each simulation predicts similar time averages, the UDS methodology provides a smoother time distribution and tracer contour plots at specific times.

• Archives of Pharmacal Research
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• v.19 no.2
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• pp.106-111
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• 1996

Alginate microspheres were prepared by the emulsification process as a drug delivery system of ampicillin sodium (AMP-Na). The preparation parameters such as the concentration of calcium chloride, the stirring time and the amount of AMP-NA were investigated. The alginate microspheres containing hydroxypropylmethylcellulose (HPMC) were found to be generally spherical, discrete and had smoother surfaces when compared to without HPMC. However, there was no significant difference in the release profile of AMP-NA from alginate microspheres prepared with or without HPMC. The concentration of calcium chloride solution and the stirring time in the preparation of alginate microspheres influenced the aggregation of alginate microspheres. The amount of AMP-NA in alginate microspheres influenced the surface morphology and the practical drug content in microspheres.