• Transactions of the Korean Society of Mechanical Engineers
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• v.3 no.3
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• pp.104-115
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• 1979

The dynamic chracteristics of a two stage relief valve is studied theoretically and experimentally. The equations of motion of spools are derived and solved by digital compter simulation to find the stiability criteria.It is shown that the area of main spool head gives damping effect to the system and that the flow pressure-coefficient of the orifice in main spool is one of the most important parameters to determine stability and response. The experimental resuls are in good atreement with the theoretical results.

• The korean journal of orthodontics
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• v.23 no.4 s.43
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• pp.485-492
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• 1993

Multiloop Edgewise Archwire(MEAW) is effective in relief the Curve of Spee in mandibular arch but up Sl down orthodontic elastics must be used with it. The purpose of this study was to analyse the effect of orthodontic elastics, like as up & down elastics, Class II elastics, and Class III elastics, and the effect of L loop in Multioop Edgewise Archwire. 1. Intrusive force of MEAW in anterior teeth was reduced and uprighting force in premolars was increased by up & down elastics. 2. Uprighting force was significintly increased with Class III elastics in multiple L loop arch wire. 3. The force of Class II elastics made molars tip mesially and Curve of Spee deep.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.3
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• pp.149-155
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• 2011

Residual stress relief by pulse magnetic treatment is attractive because the process is carried out at room temperature and magnetic fields that are easy to produce and control can be used. This study shows that strong pulse magnetic treatment can lead to stress relaxation of structural steels instead of a conventional heat treatment process. And it makes a comparative study about pulse magnetic treatment and tempering by using Larson-Miller equation. When the specimen was subjected to a pulse magnetic treatment process the residual stress in the specimen was reduced by about 13.8%. It could be compared with tempering at $200^{\circ}C$ for 2hours by using thermal effect of Larson-Miller equation. As a result, it is considered that the pulsed magnetic treatment have an effect of the stress relation by tempering at $200^{\circ}C$ for 2 hours.

• The Journal of Korea Robotics Society
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• v.13 no.3
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• pp.157-163
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• 2018

This paper deals with the development and application of control algorithms for series elastic relief robots for rescue operations in harsh environment like disasters or battlefield. The joint controller applied in this paper has a cascade structure combining inner loop for torque control and outer loop for position control. The torque loop contains feedforward and feedback controller and disturbance observer for independent, decentralized joint control. The effect of the elastic component and motor dynamics are treated as the nonlinear disturbance and compensated with the disturbance observer of torque controller. For the collision detection, Band Designed Disturbance Observer is configured to recognize/respond to external disturbance robustly in the continuously changing environment. The controller is applied to a 7-dof series elastic manipulator to evaluate the torque tracking and collision detection/response performance.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.3
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• pp.95-103
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• 2010

This paper presents a simulation model of a double-acting high-speed pneumatic cylinder with a relief valve type cushion mechanism. The model predicts piston motion, mass flow rate, pressure and temperature time histories of cushion chamber. Of interest here is to investigate the cushioning effect of varying the piston and piston-rod diameter, cushion ring diameter and length, and stoke in cushion mechanism. As a result, this cushion mechanism is found to be adequate under high-speed driving of pneumatic cylinders. The simulation model proposed here will be very useful to analyze the dynamic characteristics and to improve or design the better cushion mechanism in high-speed pneumatic cushion cylinders.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.1
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• pp.55-62
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• 1996

The dynamic photoelastic technique has been utilized to investigate the possibility of relieving the large local singular stresses which are induce in the corner of a right angled indenter. The indenter compresses a semi-infinite body dynamically with an impact load applied on the top of the indenter. The effect of geometric changes to the indenter in terms of the diameter (d) and the location (ℓ) of the notch on the relieving of the dynamic contact stresses are investigated. A multi-spark-high speed camera with twelve sparks was used to take dynamic photographs. The contact singular stresses were found to be released by introducing the relief notch along the indenter. The optimal location and geometry of the relief notch need further experimental investigation.

• Journal of Drive and Control
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• v.12 no.4
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• pp.54-59
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• 2015

Due to the tendency to use high speed pneumatic cylinders to improve productivity, cushioning devices are adopted to decelerate the piston motion of pneumatic cylinders to reduce noise, vibration, and impact. This paper presents a comparison of the cushion characteristics of a high speed pneumatic cylinder with a relief valve type cushioning device. The system parameters selected are the damping coefficient, Coulomb friction, heat transfer coefficient, and cracking pressure of the relief valve in the air cushioning device. The integral of the time multiplied square error (ITSE) is used to quantitative measure the cushioning performance to assess the effect of varying these. The cushioning performance achieved good results when the ITSE is a minimum value. In a comparison of the piston displacement and velocity with the variations in system parameters, the heat transfer coefficients are not as significantly affected as the other. Also, the cracking pressure of the relief valve is mainly affected by the pressure and temperature in the cushion chamber.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.5
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• pp.696-704
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• 2009

In this paper, the flow characteristics through an industrial safety relief valve used to protect the crankcase room in a large-sized marine engine have been numerically investigated using the moving-mesh strategy. With the room pressure higher than the cracking one, the spring-loaded disc becomes open and then the air in the room blows off into the atmosphere, resulting in the reduction of the room pressure and then the shutoff of the disc. Numerical simulations are performed on the compressible air flow through the relief valve (${\phi}160mm$) with the initial room pressure (0.11 bar or 0.12bar) higher than the cracking one (0.1 bar). The numerical method has been validated by comparing the results with the empirical ones. Results show that the disc motion and flow characteristics can be successfully simulated using the moving-mesh strategy and depend strongly on the spring stiffness and the flow passage shape. With increasing spring stiffness, the maximum disc displacement decreases and thus the total disc-opening time also decreases. In addition, the flow passage shape makes a significant effect on the velocity and direction of the flow.

• The Korean Journal of Pain
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• v.1 no.1
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• pp.87-90
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• 1988

In recent years the use of epidural opiates has increased and although this method of pain relief has shown good results in clinical practice It is still subject to certain drawbacks, the most serious of which appears to be delayed respiratory depression. Since ketamine administered systemically is unlikely to produce respiratory depression it seemed worthwhile to investigate the possibility of exploiting the potent analgesic property to ketamine by its epidural administration. The analgesic effect of ketamine 4 mg, administered epidural space, was evaluated. The duration of pain relief varied from less than 3 hours in 20% to over 24 hours in 30% of the cases. In 62.5% of the cases pain relief exceeded 6 hours. There was no evidence of respiratory depression, and there no postoperative neurologic sequelae. The present results indicated the need for further studies to compare the efficacy and safety of epidural ketamine with the response to epidural opioids for the relief of postoperative pain.

• Journal of Korean Medicine Rehabilitation
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• v.21 no.3
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• pp.79-87
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• 2011

Objectives : The aim of this study was to observe the pain relief effect of moxibustion therapy in a patient with complex regional pain syndrome(CRPS). Methods : A male with type I CRPS, 48-year-old, who suffered from severe pain and paresthesia on his legs despite of treatments of oral medications and spinal cord stimulation was treated by indirect moxibustion following Korean medicine dianosis. Total 20 moxibustion treatments(once daily, 5 days a week, for 4 weeks) were given on the 4 acupoints(both side) where known to be effective fro the CRPS. Visual analogue scale(VAS), digital infrared thermal imaging(DITI), Beck depression index(BDI) were evaluated before and after the treatments. Pain relief, thermal changes on affected legs, and improvement of depression scale were observed after the treatments. Results : As for DITI, right thigh showed low temperature compared with left on before the treatments. While after the treatments, DITI showed similar temperature in both legs at discharge day. Conclusions : Though it is a case report, moxibustion therapy might have pain relief effect. Further rigorous case series and controlled trials are warranted.