• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.613-616
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• 2005

In general, the hollow jet valve, the fixed cone valve had been used for the urgency released or maintenance of the flow rate. Nowadays, the butterfly valve, the gate valve are applied in economic performance and operation maintenance more than the hollow jet valve, the fixed cone valve. However, in the case of butterfly valve, it should be required the strict application standard to the cavitation coefficient because the structural axis and disk were situated in pipe channel and the occurring the shock problem by Karman Vortex. And, the judgment data for choice were slight lowdown in water supply and drainage facilities standard or Japanese penstock technology standard, various standard of KOWACO etc. Therefore. there were investigated the valve inside phenomenon (cavitation, disk chattering, vibration) by velocity of flow and the stability examination of body by high velocity of flow through flow scale model test using the numerical analysis and PIV to establish the applicable extensibility of the butterfly valve for the urgency released valve.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.2
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• pp.255-265
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• 2019

In the present study, the effect of opening patterns of a flow control valve on underwater discharge systems using a linear pump was investigated numerically. For that, a improved mathematical model was developed. The improvement is to separate a middle tank from a water cylinder because the cross-section area of the inlet of the middle tank is an important parameter. To validate the improved model, calculation results were compared with a previous study. The results showed that $2^{nd}$ order or more polynomial opening patterns had an advantage over ramp opening patterns. Higher an order of polynomial resulted in wider operating limits. An escape velocity and a maximum acceleration of underwater vehicle were affected by time derivative of the cross-section area of the flow control valve. Besides, as a velocity profile of the vehicle got closer to linearity, the escape velocity got faster and the maximum acceleration got smaller. And velocities of the vehicle and piston had similar variation trend.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.2
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• pp.219-227
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• 2021

In the present study, the effect of command signals of the flow control valve on performance of underwater discharge systems using a linear pump was investigated numerically. For that, the improved mathematical model was developed. The improvement is to calculate the flow leakage between the water cylinder and the piston. Also the model of the hydraulic cylinder is simplified. To validate the improved model, calculation results were compared with experiment results. The results of the study is as follows: Double ramp command signals of the flow control valve had an advantage over single ramp signals. The parametric study on the effect of double ramp command signals on performance of the system was performed. In case of using double ramp signals, the maximum acceleration of the underwater vehicle was reduced by approximately 50 % compared with using single ramp signals.

• The Journal of the Korea Contents Association
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• v.22 no.2
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• pp.794-802
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• 2022

This retrospective study was to investigate the characteristics of unplanned readmission and factors affecting readmission within 30 days of discharge in patients who underwent heart valve surgery through electronic medical records. The participants were 423 unplanned re-hospitalization within 30 days after heart valve surgery at a tertiary hospital in Seoul from January 2018 to August 2019. A total of 48 patients (11.3%) were unplanned readmissions, and the most common causes were atrial fibrillation in 13 cases (27.1%) and pain at the surgical site in 13 cases (27.1%). Other causes were: 10 cases (20.8%) of warfarin inappropriate treatment concentration, 7 cases of general weakness (14.6%), 5 cases of hypotension (10.4%), 4 cases of pericardial effusion (8.3%), 3 cases of surgical wound infection (6.3%), 3 cases of hemorrhage (6.3%), 3 cases of high fever (6.3%), and 1 case of cerebral infarction (2.1%). Variables influencing readmission were history of cancer (OR = 2.60, 95% CI 1.13-6.03, p = .025) and the patients who went to a home rather than a hospital after discharge (OR = 2.91, 95% CI 1.33-6.36, p = .008), as a type of valve surgery, mitral valve valvuloplasty had a higher readmission rate than aortic valve replacement (OR = 1.21, 95% CI 1.21-4.98, p = .012). In order to reduce unplanned readmissions, an tailored education program is needed to enable patients and caregivers to manage their comorbid chronic diseases before discharge and assess risk factors for readmission in advance.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.6
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• pp.567-572
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• 2009

The underwater launch system using an ATP consists of five parts: compressor tank, proportional flow control servo valve, expulsion spool valve, air turbine pump, and discharge tube. The purpose of this study is to develop an underwater launch system using an ATP and to verify the validity of the system. The proportional flow control servo valve is modeled as a 2nd order transfer function. The projectile is ejected by pressurized water through the air turbine pump, which is controlled by expulsion valve. The mathematical model is derived to estimate the dynamic characteristics of the system, and the important design parameters are derived by using simulations. The computer simulation results show the dynamic characteristics and the possibility of control for underwater launch system.

• Journal of the Korean Institute of Gas
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• v.21 no.4
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• pp.70-75
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• 2017

This paper presents the FEM analysis results on the deformation behavior safety of automatic cut-off horizontal and conventional vertical gas valves. Based on the FEM analysis, the primary maximum deformation of $4.4{\mu}m$ was formed on the right end side of a valve body when the internal gas pressure was supplied on the screw port and gas discharge port of an automatic cut-off horizontal gas valve. And the secondary maximum deformation of $2.9{\mu}m$ was formed on the end side of safety valve port. This small deformation of an automatic cut-off horizontal gas valve is strongly related to the balanced design of a horizontal gas valve main body, which is composed of a screw part, gas outlet port, port for a stem and spindle shaft assembly, and safety valve port. But, the primary maximum deformation of 0.076mm was formed on the upper part of a conventional automatic cut-off vertical gas valve when the internal gas pressure was supplied on the screw port and gas discharge port. And the secondary maximum deformation of 0.055mm was formed on the left end side of a gas outlet port. This may effect on the sealing clearance of o-ring that is inserted on the groove of an automatic cut-off unit. Thus, this paper recommends an automatic cut-off horizontal gas valve compared with that of a conventional gas valve for a gas leakage free mechanism of a LPG cylinder valve.

• International Journal of Safety
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• v.3 no.1
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• pp.6-9
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• 2004

This paper deals with the noise evaluation technique of a reciprocating air-compressor and its noise reduction. The reciprocating air-compressors are widely used in the small, medium sized industrial firms, and lots of their employees are affected and irritated by their noise in the workplace. Thus, noise control actions should be taken appropriately by considering the hearing loss due to the occupational noise exposure. Lead-wrapping techniques are employed to identify the contribution of principal noise sources which are generally known as motor, belts, suction/discharge valves, moving pistons, and flow-induced noise caused by edges or discontinuities along the flow path e.g. expansions, contractions, junctions and bends etc .. As a result, main noise sources of the air-compressor can be categorized by the suction/discharge noise, valve noise, and compressed-air tank noise. Based on the investigations, mufflers are designed to reduce both the suction/discharge noise and the compressed-air tank noise. Instead of the conventional valve plate, polyethylene resin is used as a new one for the reduction of valve impact noise. In addition, attempts are made to reduce the valve noise propagation to the cylinder head and the compressor tank by using the insulation casings. As a result of the countermeasure plans, it can be achieved that the noise reduction of the air-compress is up to 10dB.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.02a
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• pp.195-209
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• 2002

• Journal of Aerospace System Engineering
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• v.15 no.3
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• pp.79-86
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• 2021

For a preliminary study on a thrust-throttleable Variable Flow Ducted Rocket, a gas generator and flow control valve were developed, and ground combustion tests were performed. The gas generator and flow control valve operated at the required performance level for parameters, such as heat-resistance, combustion-time, pressure, and temperature. The combustion characteristics of a fuel-rich solid propellant mixed with Boron/MgAl/AP, etc., were also analyzed. A Plunger-type flow control valve was designed to control the discharge flow area, and it was confirmed that the flow control valve was able to control the combustion gas flow rate and pressure. However, due to the reduction of the discharge flow area caused by adhesion of combustion products, the combustion pressure continuously increased. The analysis of the pressure increase is covered in Part 2 of this paper.

• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.75-80
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• 2002

Cycle life tests have been carried out to evaluate the influence of safety valve pressure on valve regulated lead/acid batteries under deep cycling applications. Batteries were cycled at 5 hour rates at 100% DOD, and safety valve pressure was set to 1.08 and 2.00 bar, respectively. The batteries lost 248.3 g and 235.3 g of water for each case after about 1,200 cycles, but the cyclic performances of the batteries were comparable. Most of the gas of the battery during discharging was hydrogen, and the oxygen concentration increased to 18% after 3 hours of charging. The micro structure of the positive active materials was completely changed and the corrosion layer of the positive grid was less than $50{\mu}m$, regardless of the pressure of the safety valve after cycle life tests. The cause of discharge capacity decrease was found to be water loss and the shedding of the positive active materials. The pressure of safety valve does not give little effect to the cyclic performances and the failure modes of the gelled electrolyte valve-regulated lead acid batteries.