• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.653-659
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• 2017

In this study, the complex forging process of an outer support ring was developed and the prototype was manufactured. The current process, hot forging and MCT machining, has a disadvantage of excessive material removal rates and longer machining hours. To overcome this disadvantage, a general shape is given through hot forging and the precision is achieved through cold forging. The complex forging process was developed with the minimal machining process. Forging analysis was carried out to design a forging process using the commercial program, Deform-3D. The hot and cold forging processes were set up based on the analyzed result. The mold and prototype were manufactured. Hardness, surface roughness, internal defect, the grain low line of the prototype were evaluated. The results showed no particular problems, and there were no problems in mass production. Using complex forging, the material was reduced by approximately 27 % compared to the process using hot forging and MCT machining. In addition, the production speed was improved 2.15 fold compared to that of hot forging and MCT machining. Through this study, a cost-effective process and mold design technology were established, which is expected to have positive effects on other related automotive parts production.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.3
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• pp.254-262
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• 2011

Purpose: This study aims to evaluate and prospect for current research trend and developmental perspectives via analyzing recent biomaterial coated-implants study. Materials and methods: To investigate each subject respectively, several biomaterials that are using for implant surface coating were set as 'keywords'. By these keywords, major research groups in each subject were chosen, and research trend of them was analyzed. Trend of In vivo studies that examined selected biomaterials were analyzed to evaluate commercial potential. Results: The collagen research accounted for 40% of total implant study, which was the highest, and fibronectin, BMPs (bone morphogenetic proteins) and RGD (Arg-Gly-Asp) peptides followed, which were ranked in descending order. Furthermore, figures of all four research subjects were also increased with time, especially a sharp increase in RGD research. According to the results of major research group, collagen that was combined with other organic and inorganic biomaterials was mostly examined, rather than using collagen only. Major research groups investigating BMPs mostly focused on rhBMP-2. In animal studies, collagen was used as resorbable membrane in guided bone regeneration (GBR) or drug carrier, while BMPs were used with bone graft materials or coating material for titanium implant surface. Conclusion: There is not consistency of results even in identical subjects research field. Many studies are ongoing to optimize combination between mechanical surface treatment and biomaterials such as extracellular matrix component and growth factors.

• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.302-311
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• 2023

This study was conducted to evaluate the applicability of castor oil (CSO) as a natural wood preservative. CSO was treated into wood blocks prepared with domestic and imported wood species using a vacuum-pressure method, and then treatability, leachability and decay resistance of the CSO-treated wood blocks were examined. Although CSO was penetrated effectively into wood blocks of all wood species, the CSO-treatability was the highest in Western hemlock, followed by Japanese larch (LA), soft maple and Mongolian oak due to the difference of its anatomical structure. Except for LA, the more retained, the more leached during a saline water-immersing process for 48h. The use of ethanol added to reduce the viscosity of CSO affected negatively the treatability and leachability of wood blocks. Decay resistance, which was evaluated by the weight loss of wood blocks exposed against Fomitopsis palustris (FOP) and Trametes versicolor, of the CSO-treated/leached wood blocks was superior to that of control. Especially, most of wood blocks treated with preserving solution composed of only CSO (CSO-2) did not decayed and showed a very low weight loss against FOP. The decay resistance results from CSO retained in wood blocks after leaching. The retention of CSO could identify using the observation of X-ray microscope. Length of wood strips, which were treated with CSO-2 and then immersed in saline water for 2 weeks, hardly changed in all cutting directions. In addition, weight gain and length-swelling rate of the wood strips were extremely low compared to those of control. These results indicate that moisture resistance of the wood strips was improved by the CSO treatment. It is concluded that the treatment of CSO using a vacuum-pressure method provides the decay resistance and dimensional stability of wood, and thus CSO can be used as a natural wood preservative on various indoor and outdoor circumstances.

• Journal of dental hygiene science
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• v.9 no.4
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• pp.453-459
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• 2009

The purposes of this research were to evaluate the relationships of between characteristics of noise and annoyance of dental hygienist by noise in dental clinic. To investigate the dental clinic workers' reactions to noise when occurred in dental clinic, the noise level test in dental clinic and questionnaire were taken. As a result of noise evaluation, It shows that the range of noise level was 67.7~78.3dB(A) and frequency was very high (more than 4KHz). It's seem to be begins occurrence of stamina-loss, contraction of peripheral blood vessel, decrease of adrenocortical hormones. Most of respondents were affected by noise: 67% of respondents were nervous about noise and the rest of respondents were bearable. Analysis by NR-curve showed that it was exceed the noise permit level in working space. As a result of correlation - test, the more exposed dental hygienist to noise, the more felt the unpleasantness and fatigue. It's hard to sufficient explanation to patients about the dental treatment. So it's thoughts that insufficient explanation will negative impact on the patients' satisfaction and increase competitiveness in dental clinics. To remedy a unpleasantness and fatigue of noise in dental hygienist, it's considered that making an offer the ear protection and choosing the low noise-vib. equipment and using the masking effect. Therefore, It can be provide a pleasant working environment with dental hygienist and It will have a great advantage to dental clinics to improve their competitiveness.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.1
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• pp.20-26
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• 2019

Purpose: Recently TF-adaptive movement is developed in order to increase the durability of TF files. The purpose of this study was to assess the effects of adaptive movement on durability and performance of twisted files. Materials and Methods: Resin blocks simulating artificial J-shape canals were used for this study. In TFC group, TF-adaptive ML-1 (25/.08 size) files were used to prepare the canals under continuous rotation 500 rpm/4.0 Ncm. In TFA group, TF-adaptive ML-1 (25/.08 size) files were used to prepare the canals under adaptive movement. After preparing each artificial canal, TF files were observed under dental microscope for assessing existence of unwinding, distortion, and fracture. If unwinding of flute was observed, the number of artificial canals until unwinding of flute occurs was recorded. Required time until instruments reach working length and distance of unwinded portion of files from D0 were measured. All test results were conducted by Mann-Whitney U test at a 0.05 level of significance. Results: No Ni-Ti instrument's separation was observed. Number of resin blocks until file unwinding happens and working time was significantly high in TFA group compared to TF group. Distance of distortion from D0 didn't show significant difference between TFA, TF groups. Conclusion: The number of resin blocks prepared until unwinding happens and working time were significantly high in TFA group. The location of unwinding showed no significant difference between 2 groups. Adaptive movement increased the number of canals prepared until unwinding occurs and working time of twisted files.