• 한국기계연구소 소보
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• 통권18호
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• pp.75-85
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• 1988

유압 펌프 또는 모터, 특히 레이디얼피스톤형 모터, 용 분배기는 동적인 평형상태를 유지하기 위해 양면이 완전히 똑같이 가공된 회전부재와 이 부재의 양면에 동적평형을 보조할 수 있도록 표면에 가공된 형상이 동일한 2개의 고정부재와 이 2개의 고정부재의 간격유지를 위하여 회전부재주위에 사각의 단면적을 갖는 원형링으로 이루어져 있다. 회전부재는 기본적으로 밸브부를 가지고 있으며 평형상태를 보조하기위해 밸브부의 외주에 정압베어링을 설치할 수도 있다. 2개의 고정 부재중 1개는 몇 개의 단이 있는 부재인데 이는 압력상승에 의한 볼트의 인장을 보상하기 위해 밸브케이싱과 축방향의 이동이 가능하도록 하기 위한 방법이다.

• 한국항공우주학회지
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• 제36권7호
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• pp.695-702
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• 2008

액체 로켓 엔진의 연료 공급 시스템은 다양한 원인으로 인해 유동 불안정이 발생한다. 특히 연료 공급 시스템에서 발생하는 공동 현상은 공동의 생성과 소멸로 인해 후류 쪽의 압력 및 유량의 진동을 유발하게 된다. 액체 로켓은 주 추진제로 극저온 유체를 사용하게 되는데, 극저온 유체는 온도에 민감한 성질을 갖고 있기 때문에 공동 현상의 해석에 있어 온도 변화에 대한 효과를 반드시 고려해주어야 한다. 본 연구에서는 Shyy등이 제안한 “MUSHY IDM"모델을 이용하여 극저온 유체에서 발생하는 공동 현상을 모사하였다. 이를 바탕으로 오리피스에서 발생하는 공동 현상이 유동 불안정에 어떠한 영향을 미치는 지와 오리피스 형상 변화가 후류 유동의 불안정에 끼치는 영향을 연구하였다.

• 한국생산제조학회지
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• 제21권6호
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• pp.968-975
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• 2012

ABS(Anti-skid Brake System) had been developed on purpose of most effect at breaking in limited runway. An aircraft has a large amount of kinetic energy on landing. When the brakes are applied, the kinetic energy of the aircraft is dissipated as heat energy in the brake disks between the tire and the ground. The optimum value of the slip during braking is the value at the maximum coefficient of friction. An anti-skid system should maintain the brake torque at a level corresponding to this optimum value of slip. This system is electric control system for brake control valve at effective control to prevent slip and wheel speed or speed ratio. In this study we measured the thickness of the carbon disk before and after to find its wear and it shows that carbon disk brake has higher stiffness and strength than metal disk at high temperature. In addition, thermal structural stability and appropriate frictional coefficient of the carbon disk brake prove its possible substitution of metal disk brake.

• 수산해양기술연구
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• 제36권1호
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• pp.12-24
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• 2000

The electro-hydraulic servo winch system built in a automatic tension control equipment was designed with a latent need for an advanced system in fishing operations of the inshore and coastal fishing vessels. In order to keep the constant tension condition of warp under loading, a tension control circuit was added to the servo winch system.The dynamic performance in the open loop behaviour of the designed winch system was investigated and its applicability was tested for various possibilities of load using a load generator especially developed in order to this study.The mechanical characteristics of this system is different from that of a conventional type, that is, the tension, length, line speed and drum revolution can be automatically controlled by the information from various sensors, such as torque, rpm and pressure transducers. from the experiment results, it was verified that the servo winch system has very good output and tracking behaviour for the control input signals in different operating conditions though overshoot of out 8% in the transient characteristics of torque under the load though a overshoot of about 8% in the transient characteristics of torque under the load condition can be observed when the opening of servo valve, adjustable by the input voltage between - 10 V up to 10 V, changed suddenly.Consequently, the improved fishing winch system can be effectively used as the automatic shooting and hauling equipment of low cost for small inshore and coastal fishing vessels which engage in net fishing.

• 한국항공우주학회지
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• 제39권6호
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• pp.559-566
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• 2011

본 연구에서는 적외선 윈도우의 냉각을 위해 포펫 밸브와 방사형 오리피스로 구성된 냉각장치 유로를 설계하였다. 필요한 냉각제의 양은 운용조건에 따라 달라지므로 포펫 행정거리에 따른 유동장의 유량과 윈도우 전후단 압력 변화를 유동해석을 통해 예측하고 실험을 통해 이를 확인하였다. 설계된 포펫과 방사형 오리피스 유로는 윈도우 냉각에 필요한 유량을 공급하며 윈도우 구조 강도를 만족하도록 내부 압력을 낮추고 적외선 이미지 신호의 왜곡이 없도록 아음속으로 유지하여 요구 조건을 충족시켰다. 실험으로 측정된 유량을 이용하여 윈도우에서의 송출계수와 2차원 해석결과 사이의 보정계수를 확인하였으며 이를 냉각장치의 유량제어에 사용하였다.

• International Journal of Automotive Technology
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• 제3권1호
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• pp.41-46
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• 2002

Effect of secondary air injection (SAI) on hydrocarbon reduction has been investigated in a single cylinder Sl engine operating at cold-steady/cold-start conditions. The hydrocarbon emission and exhaust gas temperature with and without catalytic converter were compared with continuous and synchronized SAIs, which injected secondary air intermittently into exhaust port. Effects of SAI location, SAI pressure, SAI timing, and location of catalytic converter have been investigated and the results are compared for both SAls with base condition. At cold-steady condition, the rate of HC reduction increased as the location of SAI was closer to the exhaust valve for both synchronized and continuous SAls. The emission of HC decreased with increasing exhaust-A/F when it was rich, and was relatively insensitive when it was lean. The timing of SAI in synchronized SAI had significant effect on HC reduction and exhaust gas temperature and the synchronized SAI was found to be more effective in HC reduction and exhaust gas temperature compared to the continuous SAI . At cold-start condition, when the catalytic converter was located 20 cm downstream from the exhaust port exit, the catalytic converter warm-up period for both SAls decreased by about 50%, and the accumulated hydrocarbon emission during the first 120 s decreased about by 56% and 22% with the synchronized and continuous SAIs, respectively, compared to that of the base condition.

• Journal of Welding and Joining
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• 제26권6호
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• pp.59-66
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• 2008

Recently, automobile parts progress with modularization, which a great many allied products are modularized. Therefore, the purpose of this study is to develope modular housing for modularization of steering gear. Generally, steering gear housing is composed of valve housing and rack housing, it is important to combine two housings. However, housing having the pipe shape is very sensitive to welding distortion, and welding trajectory is very complicated. In order to solve this subject, cooperative control by using robots was constructed. Further, we developed the dedicated system to suit modular housing based on it, and applied laser welding to there. Moreover, welding speed was controlled in the rapid curve section so that the defect in trajectory of housing was reduced to obtain sound weldment. Accordingly, produced housing by this way is presented enough withstanding pressure to $100kg/cm^2$, and roundness and straightness are measured about 10/100 and 0.9/100 respectively.

• Journal of Chest Surgery
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• 제26권1호
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• pp.36-43
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• 1993

Sixty four children [aged 2 days to 9 years] , 58 with complete transposition of the great arteries, 5 with Taussig-Bing double outlet right ventricle, and 1 with double outlet left ventricle plus left ventricular type single ventricle, have undergone anatomic correction from November 1987 to August 1992. Eleven underwent previous operations: pulmonary artery banding[7], modified Blalock-Taussig shunt[2], coarctoplasty[2], aortic arch reconstruction[1] . Of 58 patients with TGA, Type A coronary arteries of Yacoub were seen in 50[86%]. U-shaped coroanry arterial flaps were transfered to the neoaorta using trap door technique, and neopulmonary arterial tract was constructed using glutaraldehyde fixed autopericardium with Lecompte maneuver. There were 18 hospital deaths [28.1%] with no late mortality. Mean follow-up of 20.4\ulcorner11.9 months were achieved in all survivors. Postoperative cardiac catheterizations were done in 14 cases. Mean pressure gradients of pulmonary and aortic outflow tract were 15.0 $\pm$2.6 and 4.2$\pm$1.4mmHg, mild aortic valve insufficiencies were found in 2, and mean cardiac index was 5.18$\pm$0.19 L/min/M2. We conclude that we should continue anatomic correction for the complex congenital heart anomalies with the malposition of the great arteries because myocardial function seems to be well preserved, though we are still on the learning curve.

• 한국자동차공학회논문집
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• 제2권4호
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• pp.27-38
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• 1994

In this paper, a simplified model of a hydraulic actuator system for a low-band type active suspension system is derived. To reduce the order of model, time constants of each chamber in hydraulic system are neglected except that of an accumulator. And the dynamics of a spool in the pressure control valve is regarded as a first-order system. The step response and the frequency response of the simplified second-order simulation model exhibit a good agreement with those of the actual system as well as those of the tenth-order simulation model. It is possible to simplify the tenth-order model to the second-order one. The low-band type active suspension model is built up by combining of a quarter car model test rig to testify the validity of the simplified model. The experimental results of suspension characteristics show that the simplified second-order hydraulic actuator model is reasonable to describe the dynamics of the actual hydraulic actuator system for a low-band type active suspension system.

• 한국자동차공학회논문집
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• 제8권3호
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• pp.28-36
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• 2000

Spray characteristics of diesel fuel injection is one of the most important factors in diesel combustion and pollutant emissions especially in HSDI (High Speed Direct Injection) diesel engines where the interval between the onset of combustion and the evaporation of atomized fuel is relatively short, An investigation into various spray characteristics from different holes of VCO(Valve Covered Orifice) nozzles was performed and its results were compared to standard sac nozzle. The global characteristics of spray, including spray angle, spray tip penetration, and spray pattern were measured from the spray images which were frozen by an instantaneous photography with a spark light source. For better understanding of spray behavior, SMD of the fuel sprays from multi hole nozzles were measured with back light imaging while the sprays from the other holes are covered by a purpose-built nozzle cap. The investigation manifestly reveals the different spray patterns at the beginning of injection produced by VCO nozzles can be identified as three distinct types with their own macroscopic and microscopic characteristics, while macroscopic non-uniformity disappears at 0.9∼1.0ms from the start of injection.