• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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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.

• 한국군사과학기술학회지
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• 제22권2호
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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.

• 한국군사과학기술학회지
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• 제24권2호
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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.

• 한국콘텐츠학회논문지
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• 제22권2호
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• pp.794-802
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• 2022

본 연구의 목적은 심장판막 수술 받은 환자를 대상으로 전자의무기록 검토를 통해 퇴원 후 30일 내 비계획적 재입원군의 특성과, 재입원 영향요인을 규명하고자 하는 후향적 조사연구이다. 대상자는 S시에 위치한 상급종합병원에서 2018년 1월부터 2019년 8월까지 심장판막수술을 받고 포함기준에 맞는 퇴원환자 423명이었다. 비계획적 재입원 대상자는 총 48명(11.3%)이었고, 그 원인은 심방세동 13건 (27.1%)과 수술부위 통증이 13건(27.1%)으로 가장 많았고, 와파린의 치료농도가 안 맞는 경우 10건 (20.8%), 전신 위약감 7건 (14.6%). 저혈압 5건 (10.4%). 심낭삼출 4건 (8.3%), 수술상처 감염 3건 (6.3%), 출혈 3건 (6.3%), 고열 3건 (6.3%), 뇌경색 1건(2.1%)이었다. 재입원에 영향을 미치는 변수는 암의 병력 (OR=2.60, 95% CI 1.13-6.03, p=.025), 퇴원 후 거주지는 병원이 아닌 집으로 간 경우 (OR=2.91, 95% CI 1.33-6.36, p=.008), 판막수술종류로서 승모판막성형술이 대동맥판막 치환술보다 재입원률이 높았다(OR=1.21, 95% CI 1.21-4.98, p=.012). 비계획적 재입원 감소를 위해 환자와 돌봄 제공자에게 퇴원 전 만성질환병력관리와 재입원의 위험 요인을 미리 사정하고 병원 방문할 수 있도록 하는 개별화된 교육프로그램이 필요하다.

• 제어로봇시스템학회논문지
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• 제15권6호
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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.

• 한국가스학회지
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• 제21권4호
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• pp.70-75
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• 2017

본 연구에서는 차단기능형 수평식 가스밸브와 기존 수직식 가스밸브의 변형거동 안전성을 FEM으로 해석하였다. FEM 해석결과에 의하면, 차단기능형 수평식 가스밸브의 나사부와 가스방출구에 가스내압이 작용할 때 밸브몸체의 우측 끝단부에서 최대 변형량 $4.4{\mu}m$가 발생하였다. 두 번째로 큰 변형량 $2.9{\mu}m$는 안전밸브가 설치된 포트의 끝단부에 형성된 것으로 나타났다. 이렇게 작은 변형량이 발생한 것은 나사부, 가스방출구, 스템 및 스핀들 축이 장착되는 포트, 안전밸브 포트로 구성되는 수평식 가스밸브의 평형이 잘 이루어지도록 설계되었기 때문이다. 반면에 나사부와 가스방출구에 가스내압이 작용할 때, 기존 차단기능형 수직식 가스밸브의 상단부에서 최대 변형량 0.076mm가 형성된 것으로 나타났다. 가스유출구의 좌측 끝단부에서 두 번째로 큰 최대 변형량 0.055mm가 발생하였다. 이러한 변형량은 차단기능형 안전장치의 그루브에 삽입된 오링의 밀봉간극에 영향을 미칠 가능성이 높다. 따라서 본 연구에서는 LPG 용기용 가스밸브의 가스누출을 완벽하게 차단할 수 있는 메커니즘을 갖춘 차단기능형 수평식 가스밸브가 수직식 가스밸브에 비해 우수하다할 수 있다.

• International Journal of Safety
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• 제3권1호
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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.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 금형가공 심포지엄
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• pp.195-209
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• 2002

• 항공우주시스템공학회지
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• 제15권3호
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• pp.79-86
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• 2021

추력조절이 가능한 가변유동형 덕티드 로켓(VFDR; Variable Flow Ducted Rocket)의 기초연구 목적으로 가스발생기와 유량조절장치를 개발하여 지상연소시험을 수행하였다. 연소시험을 통하여 본 개발에 대한 내열성, 연소시간, 압력 및 온도와 같은 성능 요구조건의 충족 여부를 확인하였으며 Boron/MgAl/AP 등을 혼합한 연료농후 고체추진제의 연소특성을 분석하였다. 유량조절장치는 Plunger 타입으로 개발하여 토출면적 조절로 유량 및 압력을 제어할 수 있음을 확인하였다. 그러나 토출 유로 내 연소 생성물 부착으로 인한 토출면적 감소에 따라 압력 안정화 구간 없이 연소압력이 증가하는 경향을 나타내었다. 토출면적 감소로 인한 압력증가의 연소특성 분석은 본 논문의 Part 2에서 다루어진다.

• Bulletin of the Korean Chemical Society
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• 제23권1호
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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.