• Journal of the Korean Geosynthetics Society
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• v.10 no.2
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• pp.1-12
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• 2011

In order to analyze the influence of particle bonding and crushing on the characteristics of shear behavior, especially residual shear behavior of granular soil, ring shear test was simulated by using DEM(Discrete Element Method)-based software program PFC(Particle Flow Code). Total four models including two non-crushing models and two crushing models were created in this study by using clump or cluster model built in PFC. The applicability of Lobo-crushing model proposed by Lobo-Guerrero and Vallejo(2005) was investigated. In addition, the results of ring shear test were analyzed and compared with those of direct shear test. The results showed that the modelling of ring shear test should be conducted to investigate the residual shear behavior. The Lobo-crushing model cannot be applied to investigate the residual shear strength. Finally, it can be concluded that the numerical models excluding Lobo-crushing model suggested in this study can be used extensively for other studies concerning the residual shear behavior of granular soil including soil crushing.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.7
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• pp.591-595
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• 2015

The roller rig tester for safety performance evaluation of wheel derailment is a test facility which can give the test load condition to the test wheel, similar to the actual dynamic condition in actual running condition. This study describes the evaluation result on the durability of the resilient wheel equipped with the ring damper and the damping material, and installed in the half part of a full scaled bogie in combination with the primary spring when it rotates under the dynamic condition. The evaluation result on durability of resilient wheel after load test of 2 million cycles shows that the safety of wheel is not affected by the applied load in visual inspection and nondestructive test, however, in the bolt used for fastening the ring damper to the wheel the loosening was found. Accordingly the use of self-locking nut and washer is recommended.

• Journal of the Korean Society of Radiology
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• v.12 no.1
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• pp.65-70
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• 2018

Computed tomography system is widely used on various fields because section image of an object can be acquired. During several step to obtain section image, artifacts by many error factors can be added on the image. Ring artifact induced by the CT system is examined in this study. A test phantom of $512{\times}512$ size was constructed numerically, and the ring artifact was investigated by the algebraic reconstruction technique. The computer program was realized using Visual C++ under the fan beam geometry with projections of 720 and detector pixel of 1,280. The generation of ring artifact was verified by applying different detection efficiency on detector pixels. The ring intensity became large as increasing the ring value, and the ring artifacts were strongly emphasized near the center of the reconstructed image. The ring artifact may be eliminated by tracking the position of ring artifact on the reconstructed image and by calibrating the detector pixel.

• Tribology and Lubricants
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• v.36 no.5
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• pp.253-261
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• 2020

In this paper, we present an experimental investigation of the frequency characteristics and a visual inspection of an oxidizer pump with a modified rear-floating ring seal for a 7-tonf turbopump. An oxidizer pump typically operates at high rotational speeds and under cryogenic conditions. Despite its low hydraulic efficiency, the floating ring seal is frequently employed as a leakage control solution for turbomachinery because it effectively reduces abrasion by friction. When the oxidizer pump starts up, the floating ring moves excursively but locks up stably against the pump casing when the contact pressure increases. The compressive force on the floating ring depends on the hydrodynamic forces induced by the flow through the floating ring. This force is controlled by the nose position of the floating ring. Based on a validation test for a 7-tonf turbopump with two types of floating rings, we concluded that the floating ring with a small diameter nose can move easily with a low contact pressure in the cooling path. This leads to instability of the pressure fluctuation around the floating ring. In contrast, a floating ring with a large diameter nose has a high contact pressure and attaches strongly to the casing, which causes wear and frictional oxidation between the contact surfaces of the impeller and the floating ring.

• Aerospace Engineering and Technology
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• v.9 no.2
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• pp.31-35
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• 2010

The Ring Laser Gyroscope makes use of the Sagnac effect within a resonant ring cavity of a He-Ne laser and has more accuracy than the other gyros. The space launch vehicle use require the high accuracy Gyro to control and determine the altitude to deliver the satellite in the space. In this paper, The theory of the Path Length Control is explained. The electrical design of Path Length Controller is described. The Design for Path Length Controller is composed of the demodulator, integrator, phase shifter, high voltage amplifier. We apply the circuit to 28cm square ring laser gyro and get the test results.

• Proceedings of the IEEK Conference
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• 2009.05a
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• pp.341-343
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• 2009

The Ring Laser Gyroscope makes use of the Sagnac effect within a resonant ring cavity of a He-Ne laser and has more accuracy than the other gyros. The Low Earth Orbit satellite for observatory use require the high accuracy Gyro to control and determine the altitude because of the need of payload pointing accuracy. In this paper, The theory of the Path Length Control is explained. The electrical design of Path Length Controller Is described. The Design for Path Length Controller is composed of the demodulator, integrator, phase shifter, high voltage amplifier. We apply the circuit to 28cm square ring laser gyro and get the test results.

• Applied Microscopy
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• v.17 no.1
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• pp.16-28
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• 1987

Carlaviruses were isolated from naturally infected medicinal plants, and identified by means of test plants and electron microscopy. Mottle symptoms were shown on leaves of Panax ginseng, Aralia cordata, Xanthium strumarium, Taraxacum officinale, Aconitum carmichaeli, and Bupleurum longiradiatum var. breviradiatum. Ring spot on leaves of Abutilon avicennae and ring mosaic or vein clearing on leaves of Sambucus sieboldiana were also shown. These viruses had rather narrow host ranges by mechanical inoculation. The virus particles were scattered or aggregated in cytoplasm of infected host plant leaves. The carlaviruses for which the name panax virus S (PaVS), aralia virus S (ArVS), xanthium mottle virus (XaVS), taraxacum virus S (TaVS), aconite mottle virus (AcMV), bupleurum virus S (BuVS) and abutilon ring spot virus (AbRSV) were proposed, had flexuous particles with width 13 nm and length $620{\sim}720nm$. A reported elder ring mosaic virus was isolated from leaves of Sambucus sieboldiana with ring mosaic or vein-clear symptoms.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.10a
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• pp.271-274
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• 2000

Despite the increasing necessity of accurate estimation of ring-stiffened cylinders' ultimate strength, the complex structural behavior of cylinders has made their design mainly depend on empirical formulas mostly based on insufficient test data rather than theoretical background. This paper has developed the imperfection method which enables the ultimate strength analysis of buckling sensitive structures by combining two general functions of common commercial finite element softwares, linear elastic buckling analysis and nonlinear stress analysis. Developed method was applied to two of the world most renowned commercial softwares, MSC/NASTRAN and ABAQUS, for the analysis of ring-stiffened cylinders and unexpectedly big difference in their analysis results was found. This tells that many widely used commercial softwares has their different strong points and week points and the choice of commercial software should be cautiously made after thorough inspection. This paper ends with some useful information about which of the aforementioned two softwares is more appropriate respectively for linear elastic buckling analysis and ultimate strength analysis of ring-stiffened cylinders.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.2
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• pp.256-260
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• 2008

The Ring Laser Gyro makes use of the Sagnac effect within a resonant ring cavity of A He-Ne laser and has more accuracy than the other Gyros. The Low Earth Orbit satellite for observatory use require the high accuracy Gyro to control and determine the altitude because of the need of payload pointing accuracy. In this paper, The theory of the Path Length Control is explained. The electrical design of Path Length Controller is described. The Design for Path Length Controller is composed of the demodulator, Integrator, Phase shifter, High Voltage Amplifier. We apply the circuit to 28cm square ring laser gyro and get the test results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.9
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• pp.1584-1588
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• 2008

The Ring Laser Gyroscope makes use of the Sagnac effect within a resonant ring cavity of a He-Ne laser and has more accuracy than the other gyros. The Low Earth Orbit satellite for observatory use require the high accuracy Gyro to control and determine the altitude because of the need of payload pointing accuracy. In this paper, The theory of the Path Length Control is explained. The electrical design of Path Length Controller is described. The Design for Path Length Controller is composed of the demodulator, integrator, phase shifter, high voltage amplifier. We apply the circuit to 28cm square ring laser gyro and get the test results.