• The Journal of Advanced Prosthodontics
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• v.8 no.1
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• pp.9-15
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• 2016

PURPOSE. Although magnetic attachment is used frequently for overdenture, it is reported that attractive force can be decreased by abrasion and corrosion. The purpose of this study was to establish the clinical basis about considerations and long term prognosis of overdenture using magnetic attachments by investigating the change in attractive force of magnetic attachment applied to the patients. MATERIALS AND METHODS. Among the patients treated with overdenture using magnetic attachments in Dankook University Dental Hospital, attractive force records of 61 magnetic attachments of 20 subjects who re-visited from July 2013 to June 2014 were analyzed. Dental magnet tester (Aichi Micro Intelligent Co., Aichi, Japan) was used for measurement. The magnetic attachments used in this study were Magfit IP-B Flat, Magfit DX400, Magfit DX600 and Magfit DX800 (Aichi Steel Co., Aichi, Japan) filled with Neodymium (NdFeB), a rare-earth magnet. RESULTS. Reduction ratio of attractive force had no significant correlation with conditional variables to which attachments were applied, and was higher when the maintenance period was longer (P<.05, r=.361). Reduction ratio of attractive force was significantly higher in the subject group in which attachments were used over 9 years than within 9 years (P<.05). Furthermore, 16.39% of total magnetic attachments showed detachment of keeper or assembly. CONCLUSION. Attractive force of magnetic attachment is maintained regardless of conditional variables and reduction ratio increased as the maintenance period became longer. Further study on adhesive material, attachment method and design improvement to prevent detachment of magnetic attachment is needed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.605-610
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• 2004

Solid propellants allow thrusters to be light-weight, com-pact and robust because they require neither tank nor valve, Moreover, the solid propellant will not leak, spill or slosh. Consequently, the solid propellant thruster is one of the potential candidates for the microthruster. On the other hand, the control of the solid propellant combustion is difficult, since the conventional solid propellant continues to bum until all the stored propellant is consumed. Although particular devices like thrust reverser were designed to control the combustion, these devices were rarely used in the practical rocket motors. These devices rise thruster weight as well as complicate the thruster operation. In this study, a solid propellant microthruster using laser sustained combustion was designed in order to develop a high-efficiency microthruster overcoming the previously-mentioned difficulty. This designed thruster has semiconductor lasers and non-self-combustible solid propellants in addition to the conventional solid propellant thruster. In this designed thruster, the semiconductor laser controls the combustion of the non-self-combustible solid propellant. In order to demonstrate that the solid propellant combustion is controllable with laser, some non-self-combustible solid propellants were irradiated with the laser at a back-pressure of about 1㎪. A 40-W class Neodymium Yttrium Aluminum Garnet (ND:YAG) laser was used as a tentative alternate to the semiconductor laser. This experiment has shown that the solid propellant combustion was controllable with 10- W class laser irradiation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.2
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• pp.360-364
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• 2016

The rare earth output is concentrated in limited number of countries including China. Also the necessity for development of non-rare earth motor is getting signified due to the rapid increase of rare earth price and resource weaponizing policies. Non-rare earth motor is generally designed as spoke type PMSM (Permanent Magnet Synchronous Motor) in order to maximize the power density. Such spoke type PMSM has advantage in concentrating the flux but demonstrates lower efficiency compared to permanent magnet using Nd (Neodymium) permanent magnet. Therefore, applications with strong necessity for efficiency need rotor structure having improved efficiency compared to spoke type PMSM. Hence, this study suggested fan-shape type PMSM with somewhat lower power density but maximized efficiency. Fan-shape type PMSM is a rotor shape demonstrating outstanding reduction of iron loss compared to existing spoke type. Thus, this study analyzed the improvement of efficiency and reduction of loss arising from the suggested shape through parameter calculation.

• Tuberculosis and Respiratory Diseases
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• v.76 no.3
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• pp.141-145
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• 2014

Although endobronchial hamartoma is a rare benign tumor, most patients with endobronchial hamartoma have respiratory symptoms such as obstructive pneumonia, hemoptysis, cough, or dyspnea due to bronchial obstruction. It can cause irreversible post-obstructive pulmonary destruction, thus early diagnosis and treatment is very important. Recently, there have been cases of neodymium-doped yttrium aluminum garnet (Nd:YAG) laser and electrocautery procedures for bronchoscopic treatment of malignant or benign central airway obstruction with comparable therapeutic efficacy and few complications. Bronchoscopic cryotherapy is a newly developed technique for management of central airway obstruction. Moreover, it provides diagnostic methods with improving diagnostic yield and safety. We report two cases of endobronchial hamartoma, each diagnosed and definitively treated with bronchoscopic techniques. Endobronchial biopsy and removal was successfully performed by cryotherapy via flexible bronchoscopy without notable complications. Follow-up bronchoscopic examinations excluded residual or recurrent disease.