• Journal of Technologic Dentistry
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• v.43 no.3
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• pp.84-92
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• 2021

Purpose: The purpose of this study was to compare the dimension safety evaluation between a general ultrasonic cleaner and an ultrasonic cleaner equipped with UV-C (ultraviolet-C). Methods: An edentulous model was prepared. A denture base and an occlusal rim were fabricated, and scanning was performed. After scanning, a denture base and full arch artificial teeth were designed. The full arch artificial teeth were printed using a three-dimensional printer (n=10). The residual resin was washed with alcohol and then scanned (reference data). The printed specimens were classified and cleaned using a general ultrasonic cleaner (GU group) and an ultrasonic cleaner equipped with UV-C (UC group). After each washing, a rescan was performed (scan data). Reference data and scan data were superimposed using overlapping software. Data were statistically analyzed using the Mann-Whitney test (α=0.05). Results: In the deviation values of full arch artificial teeth, the GU group showed a high deviation of 18.02 ㎛ and the UC group showed a low deviation of 15.02 ㎛. The two groups demonstrated a statistically significant difference (p<0.05). Conclusion: Full arch artificial teeth prepared using photopolymerized resin were deformed according to the temperature of water generated in the ultrasonic cleaner. It is judged that there is no deformation according to the UV-C ultrasonic cleaner.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.29 no.1
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• pp.25-34
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• 2020

In recent years, as a burden on tooth preparationduring the processing the laminate veneer treatments to enhance aesthetics, the interests and demands for non-prep laminate veneers are increasing which do not require teeth preparation. Although there are clear limitationsbecause the restorations are fabricated without tooth preparation, there is a clear advantage of non-invasivehealthy teeth. When manufacturing a non-prep laminate veneer, an effective design should be selected according to the aesthetic requirements and intraoral condition because the margin of restorationsshould be determined on the natural tooth surface that isnot prepared. In this article, I would like to presentthe three different designsaccording to the range which teeth are covered, and the advantages and disadvantages of them. Non-prep laminate veneer introduced in this article was fabricated using Lithium disilicate press ingot.

• Journal of Technologic Dentistry
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• v.43 no.1
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• pp.1-5
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• 2021

Purpose: To perform a comparative study on curing shrinkage according to the thickness of photopolymerization resin. Methods: Stainless steel molds of 2, 4, and 6 mm heights were prepared. The 2, 4, and 6 mm-height molds were classified as the 2H, 4H, and 6H groups, respectively. A photopolymerization resin was injected into the stainless steel mold. Photopolymerization was carried out using a photopolymer machine. During photopolymerization, the wavelength and intensity of 400~405 nm were set to 10, the highest intensity among 1~10. Photopolymerization was performed for 30 min per specimen (each group=10). The inner and outer areas of the specimen were measured. The data were analyzed using one-way ANOVA and Kruskal-Wallis H test (α=0.05). Results: In terms of the inner and outer diameters of the photopolymerization resin specimen, the 2H group contracted the most, whereas the 6H group contracted the least. A statistically significant difference was found between the groups (p<0.05). Conclusion: The amount of light irradiation of the photopolymerization resin must be adjusted according to the thickness.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.3
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• pp.214-220
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• 2022

This paper proposes a test device designed for developing a high-voltage multilayer ceramic capacitor (MLCC). The proposed topology consists of an energy recovery circuit for charging/discharging capacitor, a flyback converter, and a boost converter for supplying power and a bias voltage application to the energy recovery circuit. The energy recovery circuit designed with a half-bridge converter has auxiliary switches operating before the main switches to prevent excessive current from flowing to the main switches. A prototype has been designed to verify the reliability of target capacitors following the voltage fluctuation with a frequency range below 65 kHz. To conduct high root mean square (RMS) current to the capacitor as a load, the MLCC test was conducted after the topology verification was completed through the film capacitor as a load. Through the agreement between the RMS current formula proposed in this paper and the MLCC test results, the possibility of its use was demonstrated for high-voltage MLCC development in the future.

• Journal of Drive and Control
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• v.20 no.4
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• pp.80-91
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• 2023

The purpose of this study is to suggest the direction for the development of intelligent agricultural machinery technology in the Republic of Korea. For this purpose, intelligent technology of agricultural machinery was divided into autonomous agricultural machinery and tractor-implement intelligent communication technology. Then, a survey and analysis of a previous study of the Republic of Korea and foreign countries were conducted. GNSS-based autonomous driving technology is still widely used worldwide, and recently, as research on camera and LiDAR-based autonomous driving is actively progressing, autonomous driving technology is becoming more advanced. ISOBUS-based technology is being developed worldwide for intelligent control of tractor-attached implements, and major global agricultural machinery manufacturers are actively applying it to their products. However, although some ISOBUS technologies are being researched in the Republic of Korea, there are no cases of application on agricultural machinery yet. Therefore, to be globally competitive in the agricultural machinery manufacturing industry, there is an urgent need to advance autonomous driving technology and commercialize agricultural machinery using ISOBUS technology.

• Journal of Technologic Dentistry
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• v.13 no.1
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• pp.79-97
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• 1991

To improve the management of dental laboratory through the research on the actual condition, this study posed questions on 36 dental laboratories. The results are as follows : 1. The establishment of dental laboratory in Chunbuk was increased between in 1980 and 1986. Especially it has been more increased since 1989. According to the proportion of population the number of the dental laboratories in Chunbuk was much more than that of other provinces and took the first place in september 1990. 2. The ratio between the unlicensed dental technician and the licensed was 24.83% and 67.11% each . The former must be replaced by the licensed. And the latter ought to try to improve their culture and technique. 3. Overtime payment must be paid for those who work above eight hours. 4. It takes 5 days at a minimum for the production of dental prosthesis with both stability and esthetics. 5. Every Saturday afternoon, Sunday and national holiday must be free. 6. Bonus must be paid 600% a year at a minimum. The system of retirement allowance should be active. All dental technicians ought to be affliated with their labor union and medica insurance. 7. Such dental restoration as porcelain and crown and bridge prosthesis must by increased to a degree between 30% and 50% at a minimum and the reduction system of charge for a dental technique has to be abolished. 8. The general working conditions of dental laboratory, especially pay and working hour must be improved. 9. To advance the service improvement of dental treatment and the banishment of illegal one, the medical insurance of crown and bridge prosthesis must be generally practised. 10. Ill case of the staff cull:lloyulent of dental laboratory, minimem wage system must be observed. 11. Directing dentist system on the ertablisment of dental laboratory must be abelished or wholly improved.

• Journal of Technologic Dentistry
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• v.32 no.3
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• pp.221-232
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• 2010

Purpose: It is necessary for dental technicians exposed to hazardous chemicals in the dental laboratories to be informed of the various harmful effects of chemicals for their health and safety. The purposes of this study was to investigate the actual condition of the use of MSDS in dental laboratories and the recognition rate of MSDS for dental technicians. Methods: 231 dental technicians who were self-written questionnaire. The results were analyzed by SPSS 12.0. The answers to the questionnaire underwent frequency analysis, chi-square test and correlation analysis were performed to investigate association between health effects and recognition rate of chemical information. Results: The results from the effects of damage caused by chemicals 60.7%, and when it was less than 2 years working experience 47.6%. Currently any dental laboratories(rooms) was not furnished MSDS(0%) and even similar data furnishing rate was only 17.3%. Answer rate of 'Do not know about MSDS' was 73.6%. In addition to, education in the types and characteristics of chemicals(74.5%) does not receive all the higher education. For the question of 'To prevent human risks and accidents, is to provide chemical information needed', the answer rate of 'needed' was 87.2%. Moreover, the answer rate of 'To provide chemical information that could prevent accidents' was 76.6%. Therefore it was found that dental technicians need to be provided for chemical information. In addition, they wanted to get education related to chemicals used in the workplace(80.5%), and 90.9% was answered that they was willing to keep MSDS in they workplace. Conclusion: This study investigated the current dental laboratories(rooms) and the MSDS for the awareness and recognition of workers was very low, education was not being conducted properly. The dental laboratories(rooms) of the compact characteristics of the MSDS was not reasonably accessible and the furnishing location, dental laboratories(rooms) for the real item was needed for improvement. MSDS for dental technicians through education and promotion of information about chemicals and chemicals was to prevent health problems caused by the MSDS that will raise awareness of the necessity.

• Geotechnical Engineering
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• v.2 no.3
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• pp.27-36
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• 1986

To investigate the seepage effect on the compacted backfill of retaining walls, an expriment and an analytical study were carried out First, the expriment was performed with a two-way permeameter newly designed for the do- termination on the degree of permeability anisotropy of compacted soils. As a result, e-log(kz/ky) plot showed a linear relationship, where kz and ky were permeability coefficients for the normal and the parallel directions to the compaction. The degree of permeability anisotropy, kz/ky was 2 to 4 at Dr>90% for sands, regardless of the methods of compaction. The kz/ky of the fine sand was greater than that of the coarse sand. Second, the exprimental results were applied to the extention of Gray's theory for the investigation of the active thrust affected by the seepage of permeability anisotropy. The active thrust was decreased with the increase in the degree of permeability anisotropy, and it It.as a little effect on wall friction.

• Journal of the Korean association of regional geographers
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• v.14 no.5
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• pp.627-641
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• 2008

There have been frequent reorganizations of administrative areas and place-names in China since 1949. These reorganizations were practiced with the two institutions 'city control over surrounding counties(shiguanxianzhi)' and 'county transform to city(shigaixian)' based on the socialist commodity supply system(gongxiaozhidu) and civil registration system(hukouzhidu). In this article I will try to discuss the influence and meaning of these reorganizations on the minority nationalities districts in frontier China. The Conclusions are as follows: The increase of the number of cities and the reorganization of the place-names in the minority nationalities districts is not the result of the increase of population or advancement of industrial structure but the result of Han people having non agriculture registration(feinongyehukou) population's increase. Therefore the reorganizations of administrative areas and place-names was a process of inclusion of the minority nationalities areas as a part of the Chinese territory(guotu) more perfective than before.

• Korean Journal of Materials Research
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• v.10 no.10
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• pp.659-664
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• 2000

To develop anode-supported tubular cell with proper porosity, we have investigated the anode substrate and t the electrolyte-coated anode tube. The anode substrate was manufactured as a function of carbon content in the range of 20 to 50 vol.%. As the carbon COntent increased, the porosity of the anode substrate increased slightly and the carbon c content with proper porosity is found to be 30 vol.%. The anode-supported tube was fabricated by extrusion process a and the electrolyte layer was coated on the anode tube by slurry coating process. The anode-supported tube was cofired successfully at $^1400{\circ}C$ in air. The porosity of the anode tube was 35%. From the gas permeation test, the anode t tube was found to be porous enough for gas supply. On the other hand, the anode-supported tube with electrolyte layer indicated a very low gas permeation rate. This means that the coated electrolyte was dense.