• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.4
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• pp.501-508
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• 2022

Required essential technique is to determine the maximum recharge pressure in the well with condition of non-ground failure for the recovery of the groundwater. Based on the classical soil mechanics, the maximum recharge pressure was estimated with the numerical anlaysis and laboratory triaxial test. In the numerical analysis, the maximum recharge pressure is defined as the ground failure stress. The ground failure of the sand was defined as the piping and the one of the caly was to the undrained failure by the confined pressure increment. In the triaxial test, the recharge pressure in the ground was modified by the back pressure in the specimen. In case of sand, the volume strain was dramatically increased at the 93 % of the maximum back pressure, same meaning of the 0 effective stress state. In case of clay, the only radial volume strain was to reached 1.5 % without failure. Therefore, The maximum recharge pressure could be determined with the numerical analysis and triaxial test.

• Korean Journal of Oriental Medicine
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• v.14 no.1
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• pp.67-72
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• 2008

Objectives : The purpose of the study was to determine the effects of a 4 weeks Meridian Tai Ji exercise treatment on blood pressure reducing in hypertensive patients. Methods : We measured the blood pressure of 3 patients who were visited in the Gwacheon Health center from 21th November 2007 to 17th December 2007. Eligible participants had systolic blood pressure ${\geq}$ 120 mmHg or diastolic blood pressure ${\geq}$ 80 mmHg with antihypertensive drug. Blood pressure measurements were after the patient had been in rest for at least 10 minute. Twelve sessions of Meridian Tai Ji exercise treatment over 4 weeks were performed in the patients. Blood pressure were measured twice before and after each session. Results : After 4 weeks, blood pressure reduction was observed in the treatment patients, with an average decline of systolic blood pressure up to 5.67 mmHg and diastolic blood pressure up to 0.17 mmHg. But, it was not statistically significant. Blood pressure increased between measurements taken before and after an Meridian Tai Ji exercise treatment session, although individual responses were quite variable. No significant difference was found in the immediate effect. Conclusion : Twelve sessions of Meridian Tai Ji exercise treatment do not seem to control hypertension. Further research is required to determine whether Meridian Tai Ji exercise treatment can enhance clinical management of hypertension if it is used in combination with more enrolled participants, over longer periods, or randomized controlled trial.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.3
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• pp.299-308
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• 2011

In this study, we develop a pressure observer to measure the cylinder length of a harbor-construction robot. For the robot control, sensors are required to measure the length of a hydraulic cylinder. The cylinder-position sensor is relatively expensive when the operating environment prohibits external approaches for the measurement of the cylinder position. LVDT or linear scales are usually mounted on the outside of the cylinder, which causes poor durability on a construction site. We use a pressure sensor to indirectly estimate the length of the cylinder. The pressure sensor is mounted inside a hydraulic valve box so that it is protected by the box and easy to waterproof for an underwater robot. By treating oil as a compressible fluid, we derive the nonlinear pressure dynamics as a function of the cylinder position, velocity, and pressure. The recursive least squares (RLS) algorithm is applied to identify the dynamic parameters, and the pressure observer estimates the cylinder position through the pressure acting on the head and the rod of the hydraulic cylinder. The position accuracy is relatively low, but it is acceptable for a construction robot that handles large armor stones.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3003-3008
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• 2007

Critical nozzle has been frequently employed to measure the flow rate of various gases, but hydrogen gas, especially being at high-pressure condition, was not nearly dealt with the critical nozzle due to treatment danger. According to a few experimental data obtained recently, it was reported that the discharge coefficient of hydrogen gas through the critical nozzle exceeds unity in a specific range of Reynolds number. No detailed explanation on such an unreasonable value was made, but it was vaguely inferred as real gas effects. For the purpose of practical use of high-pressure hydrogen gas, systematic research is required to clarify the critical nozzle flow of high-pressure hydrogen gas. In the present study, a computational fluid dynamics(CFD) method has been applied to predict the critical nozzle flow of high-pressure hydrogen gas. Redlich-Kwong equation of state that take account for the forces and volume of molecules of hydrogen gas were incorporated into the axisymmetric, compressible Navier-Stokes equations. A fully implicit finite volume scheme was used to numerically solve the governing equations. The computational results were validated with some experimental data available. The results show that the coefficient of discharge coefficient is mainly influenced by the compressibility factor and the specific heat ratio, which appear more remarkable as the inlet total pressure of hydrogen gas increases.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1159-1165
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• 2011

This paper presents ride comfort characteristics of a quarter-vehicle magneto-rheological(MR) suspension system with respect to different tire pressure. As a first step, controllable MR damper is designed and modeled based on both the optimized damping force levels and mechanical dimensions required for a commercial full-size passenger vehicle. Then, a quarter-vehicle suspension system consisting of sprung mass, spring, tire and the MR damper is constructed. After deriving the equations of the motion for the proposed quarter-vehicle MR suspension system, vertical tire stiffness with respect to different tire pressure is experimentally identified. The skyhook controller is then implemented for the realization of the quarter-vehicle MR suspension system. Finally, the ride comfort analysis with respect to different tire pressure is undertaken in time domain. In addition, a comparative result between controlled and uncontrolled is provided by presenting vertical RMS displacement.

• Journal of the Korean Institute of Gas
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• v.22 no.5
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• pp.100-106
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• 2018

pressure buried pipes in domestic industrial estate have many long-term use pipes, Toxic, flammable, Inflammable, etc. as well as a variety of toxic chemicals are embedded in a complex be buried, A high level of safety management is required as it can damage other pipes installed nearby in the event of accidents such as various external interference. Therefore, in this study, the safety management practices of high-pressure gas distribution and urban gas distribution are utilized to derive efficient safety management methods for high-pressure gas installation piping through in-depth comparative analysis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.6
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• pp.568-572
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• 2009

We present a ternary microfluidic multiplexer unit, capable to address three flow channels using a pair of control lines with two different threshold pressure valves. The previous binary multiplexer unit addresses only two flow channels using a pair of control line with identical threshold pressure valves, thus addressing $2^{n/2}$ flow channels using n control lines. The present ternary multiplexer addressing three flow channels using a pair of control lines, however, is capable to address $3^{n/2}$ flow channels using n control lines with two different threshold pressure valves. In the experimental study, we characterized the threshold pressure and the response time of the valves used in the ternary multiplexer. From the experimental observation, we also verified that the present ternary multiplexer unit could be operated by two equivalent valve operating conditions: the different static pressures and dynamic pressures at different duty ratio. And then, $3{\times}3$ well array stacking ternary multiplexers in serial is addressed in cross and plus patterns, thus demonstrating the individual flow channel addressing capability of the ternary multiplexer. Thus, the present ternary multiplexer reduces the number of control lines for addressing flow channels, achieving the high well control efficiency required for simple and compact microfluidic systems.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.1
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• pp.1-7
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• 2013

Pneumatic cylinders are widely used to actuators in automatic equipments because they are relatively inexpensive, simple to install and maintain, offer robust design and operation, are available in a wide range of standard sizes and design alternatives. This paper presents a comparative study among the dynamic characteristics of meter-out and meter-in speed control of pneumatic cushion cylinders with a relief valve type cushion mechanism. Because of the nonlinear differential equations and a requirement for simultaneous iterative solution in a mathematical model of a double acting pneumatic cushion cylinder, a computer simulation is carried out to investigate pressure, temperature, mass flow rate in cushion chamber and displacement and velocity time histories of piston under various operating conditions. It is found that the piston velocity and pressure response in meter-in speed control are more oscillatory than with meter-out those when pneumatic cushion cylinders are driven at a high-speed. In meter-out speed control, the effective area of the flow control valve is larger than that of meter-in, and the supply pressure has to be much higher than the pressure required to move the load because it has also to overcome the back pressure in cushion chamber.

• Korean Journal of Acupuncture
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• v.29 no.2
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• pp.250-259
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• 2012

Objectives : In this study, it has aimed to search cupping therapy standardization research course by reviewing former studies. Methods : It has reviewed articles about cupping therapy, published in South Korea. Review focused on cupping therapy treating methods. Results : Articles about cupping therapy is slightly increasing. Clinical study was the most popular study method. It has most used non-bleeding cupping therapy, and bleeding cupping therapy is next. Treating time was very various and there were no tendency or trends about treating time. Pressure inside cup has used from 30 mmHg to 600 mmHg, and pressure of 600 mmHg used mostly. Conclusions : As a result of this study, it is considered that data and standard about pressure and treating time is required. And it should be focus on pressure and treating time to standardizing cupping therapy.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2009.05a
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• pp.184-189
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• 2009

The Measurement system of auto parts are currently precious ones in the case of most of them. In this paper We tried to implement low_cost equipment. There are many auto parts. Among them CCP(Canister Controlled Purge Solenoid) which have difficulties in the control of air fluid currently have been main object. According to the use of air amount. Required time to maintain vacuum air pressure constantly need three or four minutes but the aim of this development try to achieve keeping vacuum pressure within less shorter time, Under the constant air pressure, We try to develop control check system of auto parts CCP(Canister Controlled Purge Solenoid).