• Journal of the Korean Institute of Gas
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• v.9 no.3 s.28
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• pp.44-48
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• 2005

Experimental works were carried out to evaluate the service life of low pressure LPG regulators for domestic use. Experimental results showed that the operating pressure of regulators used for 7 years notably deviated from the standard value of the adjusting pressure and the lock-up pressure. Thus, it is estimated that low pressure LPG regulators have approximately 6 years of service life.

• Tribology and Lubricants
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• v.19 no.6
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• pp.349-356
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• 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
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• v.4 no.3 s.12
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• pp.29-38
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• 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 Composite Materials Conference
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• 2003.10a
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• pp.99-102
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• 2003

This paper aims to observe the micro-mechanical behaviour of tow geometry during deformation of dry woven carbon-fiber fabric. With the increment of shear angle fabric experiences 'lock-up'phenomenon. In this paper, deformation of micro-mechanical parameters such as tow interval, change in tow amplitude and wavelength are investigated. To observe the micro-deformation of the fabric structure, appropriate specimens from bias extension and biaxial tests are sectioned and observed under the microscope. It was found that different loading conditions cause geometric deferences in the tow architecture.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.10
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• pp.130-138
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• 2002

This paper presents the modeling and analysis of dynamic characteristics of hydraulic snubber in electric power plant. The nonlinear state-space model of 14th order to describe the dynamics of the snubber was established by Simulink. The simulation results show that the hydraulic snubber reacts as like the conventional shock absorbers against the high pulse shock load. The snubber also shows the peculiar characteristics to the small step load, which temporarily lock the control valves up, however maintain same steady-state pressures of all internal chambers in the long run. Two case studies for the analysis of the snubber were addressed. Practical pulse testing method was also proposed to identify the frequency response characteristics of the snubber.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.471-477
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• 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 Society of Precision Engineering Conference
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• 2011.06a
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• pp.1563-1564
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• 2011

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.12
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• pp.1541-1546
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• 2013

The stress concentration of lock-claws, which are one of the important parts for pneumatic fitting for a flexible tube connection, was investigated by finite element simulation. In this study, the generation of the local plastic deformation was predicted when the tube was hooked up to a pneumatic fitting in order to disperse the stress concentration, and design optimization was carried out using the Taguchi method. For the optimization, the outer width, bending angle, and inner radius of the lock-claws are used as main variables. As a result, their respective contribution ratios are revealed as 81.3%, 10.9%, and 1.5%. The ratio of the total stress distribution was improved by 4% compared with the initial design of the lock-claws.

• Journal of Oral Medicine and Pain
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• v.19 no.1
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• pp.93-103
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• 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 Society of Naval Architects of Korea
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• v.43 no.3 s.147
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• pp.322-330
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• 2006

Numerical calculations are carried out for flow past a circular cylinder forced oscillating normal to the free-stream flow at a fixed Reynolds number equal to 185. The cylinder oscillation frequency ranged from 0.8 to 1.2 of the natural vortex-shedding frequency, and the oscillation amplitude extended up to 20% of the cylinder diameter. IBM (Immersed Boundary Method) with direct momentum forcing was adopted to handle both of a stationary and an oscillating cylinder Present results such as time histories of drag and lift coefficients for both stationary and oscillating cases are in good agreement with previous numerical and experimental results. The instantaneous wake patterns of oscillating cylinder with different oscillating frequency ratios showed the synchronized wakes pattern in the lock-in region and vortex switching phenomenon at higher frequency ratio than the critical frequency ratio.