• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.267-271
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• 1997

In this study, swing phase dynamic simulation of above-knee prosthesis is performed. The prosthesis consists of a single axis knee mechanism and pneumatic cylinder. The numerical modelling of the prosthesis is analyzed in two dimensions. The governing equation of thermodynamical pneumatic cylinder model is applied to construct the control of lower limb during swing phase. Knee flexion angle with respect to the orifice diameter of the pneumatic cylinder is produced. This analysis will be very useful to the design of pneumatic cylinder in prosthesis.

• 에너지공학
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• 제6권1호
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• pp.52-57
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• 1997

유동방향으로 초원형 형상을 갖는 잘록한 관내의 압축성 유동에 관한 동특성을 수치적으로 연구하였다. MacCormack의 양해법, 즉 예측자/보정자 단계를 거친 시간 진행법을 이용하여 Euler 방정식의 해를 구하였는데, 관내 유동은 이차원, 비점성, 압축성 유동이라 가정하였다. 관의 직경비와 형상비가 압력분포에 미치는 영향을 광범위하게 고찰하였으며, 본 연구에서 개발한 전산프로그램을 이용한 수치 결과는 상용코드인 FLUENT를 이용한 결과와 비교하여 일치된 결과를 얻을 수 있었다.

• 한국가시화정보학회지
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• 제9권2호
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• pp.48-53
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• 2011

The shape of nozzle cross-section plays an important role in stabilizing electrospray jet. The angle of contact line is governed based on the famous Young-Laplace equation. Compared to a round nozzle that has a constant curvature along the orifice, the square nozzle has four square corner edges and four straight edges that hold the meniscus in a different manner and is of interest in this study. By utilizing both square and round capillary nozzle, we examine the effect of nozzle shape in electrohydrodynamic jetting. The ejections were recorded with a high speed camera and analyzed to examine the jetting repeatability based on dynamic movement of meniscus. The result suggests that if the corner edges are not sharp, then its effect on repeatability is also limited.

• 한국농공학회지
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• 제16권2호
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• pp.3430-3437
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• 1974

.It is very importaut to know the water consumption of crops in planning irrigation works and practicing suitable soil moisture management. For the purpose of making it clear that how much water be consumed to cultivate the Chinese cabbage, Chamber method has been applied. Main equipments in the transpiration chamber are flowers, manometer and electric thermograph. The chamber made of vynyl plate has a small entrance at the base and an exit at the top, and the ventilation in the chamber was carried out by a flower through the entrance and exit. Air-flow adjusted by an orifice manometer enters the chamber from the outside over the crop canopy through the pipe like a chimney and finally goes out to the outside. Two sets which consist of a pair of dry and wet bulb made by thermistor are installed in the entrance and exit tube, and record air temperature automatically. Evapotranspiration amount is computed from the air-flow quantity and difference in absolute humidity between at the entrance and exit of the chamber by the following equation: ET=(X2-X1)${\times}$Q where ET=evapotranspiration amount X1=absolute humidity at the entrance(g/㎥) X2=absolute humidity at the exit(g/㎥) Q=air-flow quantity(㎥) This study was carried out at the upland farm of the Institute of Agriculture Engimeering and Utilization, Suwon, Korea. from 1971 to 1973. The results obtained in this experiment are as follows: 1. The total amount of evapotranspiration of Chinese Cabbage that is cultivated in autumn is 408.1mm during growth period. 2. Chinese cabbage rapidly grows up in the second ten days of September, 40th to 50th days after seeding. At the same time, the maximum amount of evaportranspiration of Chinese cabbage is 61.6mm/10 days 3. The correlation between Pan-evaporation and evapotranspiration is high, coefficient of correlation r=0.88**, and can be shown as The following regression equation: ET=0.913E+20.273 4. Evapotranspiration is closely related with meteorological factors: r=0.85**, for insolation, r=0.76** for air temperature, respectively. 5. The percentage of evapotranspiration amount, at the beginning of growth stage, gradually increases in proportion as the Chinese Cabbage grows but is largely affected by meteorological factors after the green cover formation. 6. By Blaney and Griddle formula, evaportranspiration coefficient "K" are within from 0,85 to 1.27.

• 한국자동차공학회논문집
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• 제8권6호
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• pp.31-39
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• 2000

In this paper, characteristics of a port injection type LPG fuel system were investigated to adopt the system to a spark ignition engine through rig test. Engine combustion characteristics for limited conditions and the precise control method of LPG fuel supply were also studied. As a basic experiment, the effects and the relationships of parameters such as orifice area, fuel delivery pressure, fuel temperature and flow coefficient were established. From this, one dimensional compressible flow equation can be applied to control gaseous fuel flow rate by setting pressure difference between vaporizer and manifold to a certain range, for example about 1.2 bar in a naturally aspirated engine. The combustion analysis results of LPG engine were also compared with those of gasoline engine according to spark timing and load change. At part load and stoichiometric condition, the MBT spark timing of LPG fueled engine is retarded by 2$^{\circ}$ - 4$^{\circ}$CA compared to that of gasoline engine. On the contrary, the spark timing of LPG fueled engine can be advanced by 5$^{\circ}$- 10$^{\circ}$ CA at WOT, which results from higher Octane Number and burned fraction of LPG fuel compared to gasoline.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.953-961
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• 2011

Lumped parameter model에 오리피스의 이론식을 결합하여 강내탄도의 점화기 해석 모델을 개발하였다. 이 개발된 점화기 해석 모델을 이용하여 점화기 형상인 길이, 직경, 주입구 분포에 따른 강내탄도의 특성을 분석하였다. 포미와 초기탄저의 압력차의 결과로서 점화기 길이는 저주파 진동에 영향을 미치는 것으로 나타났고, 점화제 주입구 직경과 주입구 분포는 고주파 진동에 영향을 주는것으로 나타났다.

• 한국산업보건학회지
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• 제21권4호
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• pp.185-192
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• 2011

To predict contaminant concentrations within a multi-zone work environment, an air quality model in the work environment was developed. To do this, airflow equations on the basis of orifice equation were solved by using the Conte and De Boor scheme, and then equations for the conservation of mass on contaminant were solved by using the fourth-order Runge-Kutta algorithm. To validate the accuracy of simulated results, this model was applied to the controlled environment chamber that had been tested in 1998 by Chung KC. The comparison of predicted concentrations by this study with measured concentrations by the Chung KC indicated that the average deviations were 2.66, 3.35, and 3.15% for zone 1, zone 2, and zone 3, respectively. Also, this model was applied to a working plant with four zones. Thus, the results of contaminant concentration versus time were predicted according to the schedule of the openings operation, and case studies were done for four cases of the openings operation to investigate the interaction of airflow and contaminant concentration. The results indicated that opening operation schedules had a significant effect on contaminant removal efficiency. Therefore, this model might be able to apply for the design of ventilation schedules to control contaminants optimally.

• 한국유체기계학회 논문집
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• 제19권5호
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• pp.35-41
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• 2016

This paper deals with the design, manufacturing and test evaluation of a hydrostatic bearing applied to a hydraulic model turbine. The design parameters of a hydrostatic bearing, considering machining and assembly tolerances, and recommended values of design parameters are presented. Also the simple design procedure of a hydrostatic bearing by utilizing the reference results is proposed. In order to illustrate the utility and validity of the proposed design procedure, two hydrostatic bearings are manufactured and test evaluation of these bearings are performed. In results, the proposed design procedure can be utilized as an effective tool at the initial design screen of a hydrostatic bearing. However, the 2D bearing governing equation should be solved to obtain the optimal design of a hydrostatic bearing.

• Korean Chemical Engineering Research
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• 제55권6호
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• pp.767-770
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• 2017

Quadruple tank liquid level systems are popular in testing multivariable control systems for multivariable processes with positive or negative zeros. The liquid level system is nonlinear and it will help to illustrate the robustness of control systems. However, due to nonlinearity, it can be cumbersome to obtain process parameters for testing linear control systems. Perturbation sizes are limited for valid linearized process models, requiring level sensors with high precision. A simple method where the outlet orifice is replaced to a long tube is proposed here. The effluent flow rate becomes proportional to the liquid level due to the friction loss of long tube and the liquid level system shows near linear dynamics. It is applied to the quadruple tank system for easier experiments.

• 설비공학논문집
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• 제25권10호
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• pp.562-567
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• 2013

1D-numerical analysis of the network algorithm with the orifice equation for the relationship between pressure difference and flowrate has been mostly used to analyse leakage flow at the gap. In this study, a 3D-numerical method applying momentum loss model to the gap region in the computational domain is represented to reflect effectively the effect of leakage flow by determining the proportion of pressure difference to air passage velocity. While the 3D-numerical method is verified through the computation of the two compartments model, the numerical analysis of the stack effect in a building stairway is performed. As the temperature of air outside drops, the pressure in the upper stairway and leakage flowrate through the gap in the door rise. The change of gap area does not have an effect on pressure in the stairway for the analysis conditions.