• Journal of the Korean Society of Industry Convergence
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• v.19 no.3
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• pp.144-153
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• 2016

In this research performed on a pneumatic actuator, the air flow entering and exiting the cylinder, and the motion and deformation characteristics of the piston during operation of the actuator, were predicted. This was carried out by utilizing an FSI(Fluid-Structural Interaction) analysis technique that incorporates principles in computational fluid dynamics and structural stress analysis, and potential performance degradation factors were examined. Analysis results indicated that performance improvements could be made through design modifications. These include adding an inlet and outlet on the upper and lower sections of the cylinder in the conventional model, and increasing the number of sites for piston guide bars from three to four.

• Journal of Ocean Engineering and Technology
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• v.19 no.3
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• pp.11-17
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• 2005

The effect of frequency and amplitude of the OWC (Oscillating Water Column) motion on the nonlinear reaction forces in an air duct are studied experimentally. Experimental owe model is idealized as a simple circular cylinder with an orifice type air duct located at the middle oj the top rid. Reaction forces due to forced heave oscillation are measured and analyzed. By subtracting the effect of inertia forces and restoring forces, pneumatic damping force and added spring force are deduced. The effects of the frequency and amplitude of the heave motion are discussed. Also, the effects of solidity of the duct on the reaction forces are discussed.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.554-558
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• 2000

This paper proposes a new type of piezoactuator-driven valve system. The piezoceramic actuator bonded to both sides of a flexible beam surface makes a movement required to control the pressure at the flapper-nozzle of a pneumatic system. After establishing a dynamic model, an appropriate size of the valve system is designed and manufactured. Subsequently, a sliding mode controller which is known to be robust to uncertainties such as disturbance is formulated in order to achieve accurate regulating and tracking control of the desired pressure. The controller is experimentally realized and control performances for various pressure trajectories are presented in time domain. The control bandwidth of the valve system which directly represents the fastness is also evaluated in the frequency domain.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.212-219
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• 2004

The effect of frequency and amplitude of the OWC (Oscillating Water Column) motion on the nonlinear reaction forces in an air duct arc studied experimentally. Experimental OWC model is idealized as a simple circular cylinder with an orifice type air duct located at the middle of the top rid. Reaction forces due to forced heave oscillation are measured and analyzed. By subtracting the effect of inertia forces and restoring forces, pneumatic damping force and added spring force are deduced. The effects of the frequency and amplitude of the heave motion are discussed. Also, the effects of solidity of the duct on the reaction forces are discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.567-576
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• 2003

In this study, a robust controller to control pressure in a pneumatic pressure vessel with a long transmission line is proposed. Frequency response of transmission line using compressible fluid is changed by the flowing state of the fluid. So, it a fixed gain controller designed based on a model supposed the flowing state to a specific state, the performance of the control system could be degraded because of the modelling error. The controller designed in this study is composed of two parts. One is a feedback controller to improve a feedback characteristics and to compensate the influence of the variation of transfer characteristics of a transmission line owing to the change of flowing state and the other is a feedforward controller to regulate command fallowing performance. The experimental results with the designed controller show that the robustness of the control system is achieved regardless of the change of the model or the transmission line. Therefore, the designed controller can be utilized for the Performance improvement of a Pressure control system with a long transmission line using compressible fluid.

• Journal of Drive and Control
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• v.16 no.2
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• pp.66-71
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• 2019

In this study, flow analysis and dehumidification experiments were performed on hollow fiber membrane module to confirm the dehumidification characteristics for its different configurations. The CFD for the three different models was conducted using $30^{\circ}C$ temperature and 30%RH inlet humidity for quantitative analysis. Each model has different shape parameters i.e. the number of baffles. Comparison between flow analysis results and dehumidification experiment results revealed a percentage error of about 5%. The difference in relative humidity between the inlet and outlet for each model was calculated using flow analysis data. It was established that the difference in relative humidity of the inlet and outlet for the refined model with three baffles was highest among the three modeled modules of hollow fiber membrane module, i.e. around 9%.

• Journal of Chest Surgery
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• v.23 no.3
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• pp.438-451
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• 1990

Pneumatic total artificial heart[TAH] has been clinically applied for the purpose of permanent or temporary use followed by cardiac transplantation in the patients with end stage heart diseases. In spite of the good durability of the pneumatic TAH, thrombus formation, bleeding and infection resulted in death. The Tomasu heart, which is a type of pneumatic TAH, was used in this study. This model is a modified Jarvik heart and consists of atrial cuffs, outflow vascular grafts and thin-layer seamless diaphragm type of ventricles. Cardiac outputs of the left artificial heart were measured by Donovan`s mock circulation under variable conditions of driving parameters, and an experimental artificial heart implantation was performed in 4 calves to observe the changes of hemodynamic parameters in early postoperative period and hematologic and bio-chemical changes in a long-term survival case. In the mock circulation test, cardiac output of the heart was increased with the increase of the left atrial pressure and left driving pressure. Maximum cardiac output was obtained at the heart rate of 120 to 130/min and percent systole of 40 to 45Zo under the condition of a constant left driving pressure of 180mmHg and left atrial pressure of 10mmHg. During the first 24 hours of TAH pumping, driving pressure ranged from 178$\pm$5mmHg to 187$\pm$8mmHg for the left heart and from 58$\pm$6mmHg to 78$\pm$28mmHg for the right heart. The Mean arterial pressure significantly increased between 2 and 8 hours after the start of pumping. The survival time ranged from 27 hours to 46 days. The causes of death were respiratory failure in 2 cases, mechanical valve failure in one, and left ventricular outflow obstruction due to thrombus in a 46-day survival case. This study demonstrated that Tomasu artificial heart operated effectively during the first 24 hours of artificial heart pumping, but thrombus formation around the valve holding area was the main problem in long-term survival case.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.165-174
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• 2007

Variable displacement type piston pump uses various controllers for controlling more than one state quantity like pressure, flow, power, and so on. These controllers need the mathematical model closely expressing dynamic behavior of pump for analyzing the stability of control systems which usually use various kinds of state variables. This paper derives the nonlinear mathematical model for variable displacement type piston pump. This model consists of two 1st oder differential equations by the continuity equations and one 2nd oder differential equation by the motion equation. To simplify the model we obtain the linear state variable model by differentiating the three nonlinear equations. And we verify this linearized model by comparison of simulation with experimentation and analyze the stability for the flow/pressure control. Finally this paper suggests the design compensation to ensure the stability of the systems.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.6
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• pp.638-645
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• 2004

A new micro actuation concept is introduced and studied in this paper. This idea is based on the thermo-pneumatic actuation principle. In order to improve the performance of a conventional thermo-pneumatic actuator, the idea of bistable buckling is added. By using a membrane which has the bistable buckling characteristics, the working pressure difference can be increased and as a result the work output can be increased. The analysis model for each phenomenon, bistable buckling and phase change, are suggested and the each model is verified with experimental data. From the comparison of the theoretical prediction with the experimental results, it can be concluded that these models are useful for such micro actuator analysis.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.3 no.1
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• pp.6-12
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• 1989

Methods of voice rehabilitation in laryngectomees include training of esophageal speech, use of electrolarynx and pneumatic speech aid and surgical methods, etc. In this paper, we introduce the experimental model of obturator-type electrolarynx which has several advantages for use such as ease of learning, no disagreeable appearance, and both hands not being occupied. We compared it to normal voice and other voice rehabilitation methods such as esophageal voice, japanese pneumatic speech aid and cervical electrolarynx in intelligibility and sonagraphic evaluation. The results are as follows; 1) Obturator-type electrolarynx exhibited the lowest intelligibility. 2) In sonagraphic evaluation, the spectrogram produced by the obturator-type electrolarynx was the most different from those of normal voice.