• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.315-323
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• 2004

An electrical cascade impactor is a multi-stage impaction device to separate airborne particles into aerodynamic size classes using particle charging and electrical detection techniques. A Faraday cage and an aerosol charger, which are basic components of the electrical cascade impactor, were designed and evaluated in this study. The low-level current response of the Faraday cage was investigated with changing particle size and air flow rate by using sodium chloride (NaCl) particles. The response of the prototype Faraday cage was very similar to that of a commercial aerosol electrometer (TSI model 3068) within ${\pm}$5% for singly-charged particles. The response linearity of the prototype Faraday cage could be extended up to flow rate of 30 L/min. For the performance evaluation of the aerosol charger the monodisperse liquid dioctyl sebacate (DOS) particles, with diameters of 0.1∼0.8$\mu\textrm{m}$, were generated using spraying from an atomizer followed by evaporation-condensation process. Typical performance parameters of the aerosol charger such as P$.$n, wall loss, and elementary charges per particle were evaluated. The performance of the prototype aerosol charger was found to be close to that of the aerosol charger used in an electrical low pressure impactor (ELPI, Dekati).

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.36 no.6
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• pp.528-532
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• 2010

Introduction: There are few reports on tooth eruption through Bio-Oss grafts. To our knowledge, there are no reports on whether teeth can erupt normally through the grafts. The aim of this study was to examine the effect of Bio-Oss grafts on tooth eruption in a canine model. Materials and Methods: In five 10-week-old dogs, the deciduous third mandibular molars in one jaw quadrant of each animal were extracted and the fresh extraction sockets were then filled with Bio-Oss particles (experimental side). No such treatments were performed on the contralateral side (control side). A clinical and radiological evaluation was carried out every other week to evaluate the eruption level of the permanent third mandibular premolars and compare the eruption levels between the two sides. Results: At week 4 after the experiment, the permanent third premolars began to erupt on both sides. At week 12, the crown of the permanent third premolar emerged from the gingiva on both sides. At week 20, the permanent third premolars on both sides erupted enough to occlude the opposing teeth. No significant differences were found between the control and experimental sides in terms of the eruption speed of the permanent third molars. Conclusion: These findings demonstrate that the grafting of Bio-Oss particles into the alveolar bone defects does not affect tooth eruption.

• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2230-2237
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• 2020

Self-priming venturi scrubber is one of the most effective devices used to collect aerosols and soluble gas pollutants from gaseous stream during severe accident in a nuclear power plant. The present study focuses on investigation of dust particle removal efficiency of the venturi scrubber both experimentally and theoretically. Venturi scrubber captures the dust particles in tiny water droplets flowing into it. Inertial impaction is the main mechanism of particles collection in venturi scrubber. The water injected into venturi throat is in the form of jets through multiple holes present at venturi throat. In this study, aerosols removal efficiency of self-priming venturi scrubber was experimentally measured for different operating conditions. Alumina (Al₂O₃) particles with 0.4-㎛ diameter and 3950 kg/㎥ density were treated as aerosols. Removal efficiency was calculated for different gas flow rates i.e. 3-6 ㎥/h and liquid flow rates i.e. 0.009-0.025 ㎥/h. Experimental results depict that aerosols removal efficiency increases with the increase in throat velocity and liquid head. While at lower air flow rate of 3 ㎥/h, removal efficiency decreases with the increase in liquid head. A theoretical model of venturi scrubber was also employed and experimental results were compared with mathematical model. Experimental results are found to be in good agreement with theoretical results.

• The korean journal of orthodontics
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• v.45 no.5
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• pp.217-225
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• 2015

Objective: Three-dimensional (3D) printing is a recent technological development that may play a significant role in orthodontic diagnosis and treatment. It can be used to fabricate skull models or study models, as well as to make replica teeth in autotransplantation or tooth impaction cases. The aim of this study was to evaluate the accuracy of fabrication of replica teeth made by two types of 3D printing technologies. Methods: Fifty extracted molar teeth were selected as samples. They were scanned to generate high-resolution 3D surface model stereolithography files. These files were converted into physical models using two types of 3D printing technologies: Fused deposition modeling (FDM) and PolyJet technology. All replica teeth were scanned and 3D images generated. Computer software compared the replica teeth to the original teeth with linear measurements, volumetric measurements, and mean deviation measurements with best-fit alignment. Paired t-tests were used to statistically analyze the measurements. Results: Most measurements of teeth formed using FDM tended to be slightly smaller, while those of the PolyJet replicas tended to be slightly larger, than those of the extracted teeth. Mean deviation measurements with best-fit alignment of FDM and PolyJet group were 0.047 mm and 0.038 mm, respectively. Although there were statistically significant differences, they were regarded as clinically insignificant. Conclusions: This study confirms that FDM and PolyJet technologies are accurate enough to be usable in orthodontic diagnosis and treatment.

• Science of Emotion and Sensibility
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• v.13 no.4
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• pp.741-752
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• 2010

City culture resources are critical elements to city brand strategies for improving city attraction and provide much contribution to induce visitors from competitive city. A city brand needs to be distinguished and differentiated from competing cities because they are all engaged in the similar environment of city. The differentiation of brand achievement has become increasingly important to highlight certain brand functions to include emotional, self-expressive, and symbolic functions since the importance of such functions has been further emphasized in promoting tourism activities. In particular, That is the recent role of city brand personality that has been emphasized in city management. In other words, visitors now freely and actively express their personalities or egos in tourism activities, taking an important role in construction of a brand asset. The study examines how culture resources affect city brand personality, relationship quality, and city brand royalty in the tourism city. The authors test the proposed model using data from Jeju tourists. The pivotal findings via the structural equation model in the study are as follows; 1) culture resources have been classified culture programs, culture infra, human resources, 2) The city brand personality has been classified as innovativeness, peacefulness, sophistication, confidence and dynamics; 3) The culture resources influenced on the city brand personality; 4) The city brand personality influenced on the satisfaction and involvement; 5) The satisfaction and involvement influenced on the loyalty. Results from the empirical study indicates that culture resources have a strong positive impaction on city brand personality. To increase tourist' royalty of city brand personality, managements must manage culture effectively and create friendly city brand personality to in accord with tourist needs.