• Tribology and Lubricants
• /
• v.20 no.4
• /
• pp.183-189
• /
• 2004

The floating ring seal is used in an oxidizer and a fuel pump of the turbo pump unit in the liquid rocket engine to optimize a leakage without rubbing phenomenon. The damper floating ring seal, one of the floating ring seals, is with round hole pattern surfaces. It can reduce the leakage by increased friction factor that obtained from experimental data. In this paper, the leakage test about floating ring seal and damper floating ring seal was conducted. The test result showed the leakage performance of damper floating ring seal was better than the leakage performance of floating ring seal. With the leakage test the lock-up and rotation test about seal was conducted and that position is measured. The relatively large lock-up eccentric ratio was obtained from the test result of damping floating ring seal. The attitude angle of seal increases with increasing of shaft rotation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.820-825
• /
• 2004

The floating ring seal is used in an oxidizer and a fuel pump of the turbo pump unit in the liquid rocket engine to optimize a leakage without rubbing phenomenon. The damper floating ring seal, one of the floating ring seals, is with round hole pattern surfaces. It can reduce the leakage by increased friction factor that obtained from experimental data. In this paper, the leakage test about floating ring seal and damper floating ring seal was conducted. The test result showed the leakage performance of damper floating ring seal was better than the leakage performance of floating ring seal. With the leakage test the lock-up and rotation test about seal was conducted and that position is measured. The relatively large lock-up eccentric ratio was obtained from the test result of damping floating ring seal. The attitude angle of seal increases with increasing of shaft rotation

• Tribology and Lubricants
• /
• v.21 no.3
• /
• pp.122-129
• /
• 2005

The floating ring seal has the ability of minimizing clearance without rubbing phenomenon. However, the seal ring can be unstable due to extremely high lock-up eccentricity ratio arisen from the poor design of height and surface finish of the ring. The exact prediction of the lock-up position of the floating ring is necessary to design the floating ring properly. The governing equations are developed and solved numerically. The test facility for the measurement of the boundary-lubrication-friction coefficient of the ring‘s surface has been established. Based on the results of analysis, the geometric conditions of the floating ring seal are suggested for operating at a low lock-up eccentricity ratio.

• The Journal of Korean Society for Radiation Therapy
• /
• v.26 no.1
• /
• pp.37-42
• /
• 2014

Purpose : At the time of the pelvis cancer radiation treatment using the belly board, set-up error is large because of a prone position. In order to improve the reproducibility, we made Vac-lock type belly board. In this study, we attempt to validate its utility. Materials and Methods : We compared belly board and Vac-lock type belly board through the OBI. OBI was performed three times with entire course of treatment and the setup errors in the direction of X axis, Y axis, Z axis were recorded and calculated the distance from the isocenter. Results : X axis, Y axis, Z axis setup errors with existing belly board were 0.32 cm, 0.41 cm, 0.29 cm. The setup errors with the vac-lock type belly board were 0.12 cm, 0.19 cm, 0.17 cm. Further, errors of 0~0.29 cm were increased from 48% to 83% when using VLT belly board. Error of 0.5 cm or more was reduced from 21% to 2%. Conclusion : Vac-lock type belly board is able to maintain the efficacy of existing and create to match the characteristics of the patient. Therefore We think that vac-lock type belly board is very useful in pelvic cancer patients.

• Tribology and Lubricants
• /
• v.19 no.6
• /
• pp.349-356
• /
• 2003

A damper floating ring seal with round hole pattern surfaces is suggested for better leakage control. The flat plate test of the round hole pattern surfaces has been performed to yield an empirical friction factor model. The exact predictions of the lock­up position of the damper floating ring, the leakage performance, and the rotordynamic coefficients of the seal are necessary to evaluate the rotordynamic performance of the turbo pump unit. The governing equations including the empirical friction factor model for round hole pattern surfaces are solved by the Fast Fourier Transform method. The lock­up position, leakage flow rate, and rotordynamic coefficients are evaluated according to the geometric parameters of the damper floating ring seal. Theoretical results show that the damper floating ring seals yield less leakage and better rotordynamic stability than the floating ring seal with a smooth surface.

• The KSFM Journal of Fluid Machinery
• /
• v.4 no.3 s.12
• /
• pp.29-38
• /
• 2001

The floating ring seal has the ability of minimizing clearance without the rubbing phenomenon. It is often used in the turbo pump units of liquid rocket engines due to its superior leakage performance. The exact prediction of the lock-up position of the floating ring, the leakage performance, and the rotordynamic coefficients of the seal is necessary to evaluate the rotordynamic performance of the turbo pump unit. The governing equations(which are based on the Bulk-flow Model) we solved by the Fast Fourier Transform method. The lock-up position, leakage flow rate, and rotordynamic coefficients are evaluated according to the geometric parameters of the floating ring seal.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.471-477
• /
• 2003

The floating ring seal is often used in the turbopump (TP) unit of liquid rocket engine (LRE) owing to its inherent ability of minimizing the leakage flow and superior dynamic characteristics as well. This paper describes the test results concerned with the lock-up and dynamic characteristics of the floating ring seals in the turbopump. The characteristics of the floating ring seals were extracted from the frequency response function (FRF) by instrumental variable method. The experiment was tested at 7.0MPa and 0-24,800 rpm. And the test results were introduced about the dynamic characteristics of floating ring seal related with the eccentricity and attitude angle.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.11a
• /
• pp.186-187
• /
• 2006

The development of SFCL (Superconducting Fault Current Limiter) is getting more important as the power demand is increased rapidly. Up to now, several kinds of SFCL have been proposed and it is expected that they will be applied to appropriate position considering their own properties. Amongst those proposed SFCL, flux-lock type SFCL using the magnetic cancelation for current limiting has the advantages of overcoming the technical difficulties that other types of SFCLs have. In this paper, the integrated three-phase flux-lock type SFCL was fabricated and its operational modes were investigated through the short circuit tests. The operational mode were to divided into four mode according to the variation of the currents flowing into the secondary winding connected the superconducting elements and the speed of the quench generation. It was expected that the improvement of current limiting characteristics of the SFCL could be possible through control of the operational mode.

• Journal of Oral Medicine and Pain
• /
• v.19 no.1
• /
• pp.93-103
• /
• 1994

In order to evaluate thelong-term results of conservative treatment on TMJ closed lock, a follow-up study of thirst-two patients was performed 2 to 7 year after treatment. Evaluating method included the questionnaire, clinical examination, transcranial radiograph and mandibular kinesiography. The results were as follows : Seventy-eight percents of patients reported that symptoms were reduced completely or considerably. Recurrent headache was improved after treatment (72 percents of success rate). There was a significant decrease in VAS after treatment and at follow-up comparing with that of before treatment(p<0.01). Most common variable of Helkimo's clinical dysfunction index at follow-up was impared TMJ function. There was a significant decrease in Fricton's craniomandibular index and dysfunction index(p<0.01) Mean interincisal distance was increased by 14.07mm after treatment and was also increased at follow-up by 2.80mm comparing with that of after treatment(p<0.01). Before treatment, condylar translation measurements of affected and non-affected sides on the transcranial radiograph were 4.89±3.20mm and 9.09±3.73mm respectively and at follow- up examination, those were 14.98±4.77 and 17.05±4.35mm respectively. At follow-up, condylar translation were increased significantly comparing with those of before treatment(p<0.01). In 93.1% of patients, the condylar position of affected side at maximum mouth opening was behind the articular eminence before treatment but the percentage was decreased to 13.8% at follow-up(p<0.01). The pattern and range of mandibular movements at follow-up examination were similar to the typical normal movements. And in 16 cases showing lateral deviation of opening path, the deviation was directed to the affected and non-affected sides with the same frequency.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.7 no.4
• /
• pp.635-641
• /
• 2006

On the wireless-communication between Electronic Tag of RFID system and Reader, there are some existing problems with weaknesses of security such as spoofing, replay, traffic analysis, position tracking, etc., in the established hash-lock related algorithm. This paper has presented the comparison and analysis of the established hash-lock related algorithm for privacy and in order to make up for this, also suggested a new security authentication algorithm based on hash which has an authentication protocol and creates hash function by using random numbers received from the reader on real-time and every session. The algorithm suggested is able to make RFID wireless authentication system offer a several of usefulness and it has an advantage to reduce the amount of calculations compared to established algorithm. It also uses just the tags needed among a lot of tags around which are expected later and it is expected to reduce a responsibility of the server by ending unnecessary tags' action with time based.