• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11a
• /
• pp.379.1-379
• /
• 2002

In this paper the leakage prediction and rotordynamic analysis of an annular seal with a smooth rotor and spiral-grooved stator are performed. For developing a theoretical model, the three-control-volume analysis of the circumferentially-grooved seal is expanded by considering pressure reduction due to the pumping effect of spiral groove and pressure flow through the spiral groove. Validation to the present analysis is achieved by comparisons with available experimental data. (omitted)

• Tribology and Lubricants
• /
• v.24 no.6
• /
• pp.291-296
• /
• 2008

In order to improve the leakage prediction and rotordynamic analysis of an annular seal with a smooth rotor and circumferentially grooved stator, CFD analysis using FLUENT has been performed to determine the groove penetration angle a which is the angle of separation line between control volumes II and III in groove section of Ha and Lee's three-control-volume theory. Validation to the present analysis using new penetration angle determined by the CFD analysis is achieved by comparisons with the results of published Ha and Lee's analysis. For the leakage prediction the present analysis shows slight improvement and CFD results yields the best. Direct damping and cross-coupled stiffness coefficients are predicted better to the experimental ones. However, direct stiffness coefficient is predicted worse.

• Korean Journal of Environmental Biology
• /
• v.18 no.1
• /
• pp.145-151
• /
• 2000

The mouthparts of the Apionidae are almost of the same structures as in the Curculionidae feeding soft plant tissues, and two subfamilies in the current system are well supported by their structures. The subfamilies Apioninae and Nanophyinae are clearly characterized as follows. In Apioninae, clypeal margin sinuate; mandibles meet anteropo-steriorly when retracted and more or less curved internally; maxillary palpi two-segmented, with large palpiger; labial palpi one-segmented; prementum parallel-sided, longer than wide. In Nanophyinae, clypeal margin with two to three notches in the middle; mandibles meet anteroposteriorly when retracted and more or less curved internally; maxillary palpi three-segmented, palpiger about as great as stipes; labial palpi two-segmented, separated to each other by the apical protrusion of prementum; prementum about as long as wide. [Insecta, Coleoptera, Comparative morphology, Mouthparts, Apionidae].

• The korean journal of orthodontics
• /
• v.32 no.6 s.95
• /
• pp.455-466
• /
• 2002

The objective of this study was to evaluate the changes that occurred over time in the distracted periodontal ligament space following the rapid retraction of a tooth by periodontal distraction after bone undermining surgery had been conducted in the dogs. The upper second premolars were extracted on the left and right side in 4 male beagle dogs. Immediately after extraction, the interseptal bone distal to the upper first premolar was thinned and undermined by grooving to decrease the bone resistance. Activating an individualized distraction appliance at the rate of 0.225mm twice a day, the upper first premolar was retracted rapidly toward the extraction socket. Periodontal distractions were performed for 5, 10, and 20 days, and 20-day-distraction cases were followed by maintenance periods of 0, 14, 28, and 56 days. After 20 days of rapid retraction, the average distal movement of the upper first premolar was 5.02mm, and the average mesial movement of the upper third premolars serving as an anchorage unit was 0.18 mm. On histological examination, the regeneration of bone occurred in a highly organized pattern. Distracted periodontal ligament space was filled with newly formed bone oriented in the direction of the distraction, and this was followed by extensive bone remodeling. This result was similar to those observed in other bones after distraction osteogenesis. In the periodontal ligament, the relationship between collagen fibers and cementum began to be restored 2 weeks after the distraction was completed, and showed almost normal features 8weeks after the completion of the periodontal distraction. However, on the alveolar side, the new bone formation was still in process and collagen fiber bundles and Sharpey's fibers were not present 8 weeks after the completion of the periodontal distraction. Reactions in the periodontal ligament of the anchorage tooth represented bone resorption on the compressed side and new bone deposition on the tension side as occurred in conventional orthodontic tooth movement. In conclusion, the results of this study showed that periodontal structures on the distracted side of the periodontal ligament were regenerated well histologically following rapid tooth movement.