• Journal of the Society of Naval Architects of Korea
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• v.46 no.4
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• pp.435-443
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• 2009

Optimal duct design of a HVAC system requires analysis technology to accurately evaluate its pressure losses, flow rate and velocity for making a compromised design among fan capacity and duct size affecting initial manufacturing and operation costs, and noise induced by the HVAC system. In this paper, we carry out initial duct design using the equal friction method. Using the result, the T-method is applied for accurate analysis of flow rate. Then, the duct size is modified using the difference between the required and the calculated flow rate, which can guarantee required flow rate, reduce the pressure unbalance among duct paths and lead to select optimal fan performance. To verify the validity and effectiveness of the proposed design method, an example for HVAC system design including noise analysis is demonstrated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.191-195
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• 2006

It is definitely required to control dispersion of the rocket engine performance in order to accomplish the mission of a launch vehicle successfully. A performance dispersion analysis was conducted for a gas generator cycle liquid rocket engine and the required pressure drops were estimated for engine tunning. As a result, the vacuum thrust dispersion of the engine was from +9.1% to -8.7% and the mixture ratio deviated from +9.7% to -9.6% from the nominal value due to the errors of components and the engine inlet condition of propellants. The required pressure drop in the LOx line to the combustor is higher than in the fuel line for same mixture ratio change.

• Journal of ILASS-Korea
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• v.12 no.3
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• pp.146-153
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• 2007

The prediction of diesel spray penetration has been the subject of several works and intensive investigations are still underway by many researchers. It is required to summarize the correlations developed before 1990 days and to introduce the correlations reported recently in the literature. The existing zero-dimensional models for the prediction of diesel fuel spray penetration can be classified as theoretical and empirical correlations. Of various correlations, the models considered in this paper were selected as based on the evaluation results of previous reviews and the recently published works in the literature. The existing theoretical correlations can be classified into seven categories and the existing empirical ones as two categories in this review. According to the review of existing models, the dominating factors for the prediction of spray tip penetration are the spray angle, discharge coefficient, pressure drop across nozzle, ambient density and orifice diameter and time after the start of injection. Especially, the definition for the measurement of spray angle is different with researchers. It is required to evaluate the existing spray tip penetration models for the very high injection pressure and other fuel sprays such as DME. It is also required to evaluate the correlations for the prediction of diesel spray penetration with the connection of liquid-phase penetration.

• Aerospace Engineering and Technology
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• v.9 no.1
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• pp.125-132
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• 2010

Estimation of pressurant mass flowrate and its total mass required to maintain propellant tank pressure during propellant outflow is very important for design of pressurization control system and pressurant storage tank. Especially, more pressurant mass is required to maintain pressure in cryogenic propellant tank, because of reduced specific volume of pressurant due to heat transfer between pressurant and tank wall. So, basic model for propellant tank ullage calculation was proposed to estimate ullage and tank wall temperature distribution, required pressurant mass, and energy distribution of pressurant in ullage. Both test and theoretical analysis have been conducted, but only theoretical modeling method was addressed in this paper.

• Journal of Sensor Science and Technology
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• v.24 no.4
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• pp.239-246
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• 2015

Blood pressure is possible to diagnose a disease associated with blood pressure and judgment the current health of patients. Automatic blood pressure monitor capable of measuring a blood pressure easily in hospital and at home have become spread. In this study, we developed the blood pressure simulator (BPS) that can test the arm-type automatic blood pressure monitor that is commonly used in hospital. BPS is to produce a pressure similar to the pressure wave generated in the human blood using a servo disk motor. Then, using the silicon tube, it implements the situations such as human blood vessels, and to output the generated pressure waveform. Simply the BPS's phantom put on the cuff and it is able to simulate blood pressure. So anyone can quickly test the blood pressure monitor within one minute and it is possible to shorten the test time required for the automatic blood pressure monitor. In Performance test, the trends and the standard deviation of the values measured in the BPS is similar to the value of the measured pressure from people with normal blood pressure. Thus, the development BPS showed a possibility of taking into account the actual blood pressure measurement environment simulator.

• Korean Journal of Applied Biomechanics
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• v.15 no.1
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• pp.143-153
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• 2005

J.Y. CHOI,S. J. KIM, E. L. LEE. Change of plantar pressure Distribution of Open Stance during Forehand Strke in Tennis. Korean Journal of Sport Biomechanics, Vol. 15, No. 1, PP. 143-153, 2005. Recently among several tennis techniques forehand stroke has been greatly changed in the aspect of spin, grip and stance. The most fundamental factor among the three factors is the stance which consists of open, square and close stance and it is very important to know the patterns of plantar pressure distribution for the better understanding of forehand stroke. Therefore, the purpose of this study was to investigate the change of plantar pressure distribution in open stance during forehand stroke in tennis. Three high school tennis players were recruited for the study and required to perform forehand stroke five consecutive trials in the condition of open stance. The forehand strokes were filmed with two digital video cameras and measured with pedar system for plantar pressure. The plantar regions under the foot were divided into 3 regions, which were forefoot, midfoot, and rear foot. In conclusion, The plantar pressure of open stance during forehand stroke was distributed more largely to the right foot. The plantar pressure of open stance during forehand stroke was distributed more weight loads on forefoot of right than heel of right

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.3
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• pp.285-290
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• 2006

In a Vehicle, Safety is the most important factor for drivers. It is well known that tire pressure lower than normal reduces the safety of the vehicle. In a consideration of active safety, tire pressure monitoring system is absolutely required. Tire pressure monitoring using in-tire pressure sensors with an RE data link have proven to be best approach to measuring tire pressure over the widest range of operating conditions. In this paper, we describe the parameters of TPMS, the characteristic of tire pressure and temperature compensation. These are the main factors to design the decision logic. We will show the guidelines for TPMS logic development considering environment variables and vehicle conditions.

• Fashion & Textile Research Journal
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• v.19 no.5
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• pp.602-607
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• 2017

This study was undertaken to compare the gait characteristics between the Korean elderly and young adults, we measured the plantar pressure and contact time of gait with barefoot along a walkway at their preferred walking speed. The results indicate that older people exhibited significantly less plantar pressure than young adult in all 3 regions (FF, MF and RF) and significantly less time % on the initial contact phase (ICP), forefoot push-off phase (FFPOP) and significantly more % forefoot contact phase (FFCP) and foot flat phase (FFP). The converted plantar pressure value to percentage, it showed more pressure in forefoot (FF) in the elderly person than the young adults. It could be explained that the forward shifting in plantar pressure are associated with a more flexed posture of elderly such as actual stabilizing fearrelated adaptations. Longer total foot contact time in the elderly means that the old people show the decreased gait velocity. In other words, lower velocity was found to be associated with pre-existing fear of falling. With longer contact time and slower stepping movement, the elderly become more unstable. With these findings, it could be confirmed that there were significant changes in foot characteristics which contribute to alter the plantar pressure and contact time during gait with advancing age. Further research is required to establish possible links to risk of falling and development of footwear in the elderly adults.

• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.65-71
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• 2009

The pressure transient inside the passenger cabin of high-speed train has been assessed using computational fluid dynamics (CFD) based on the axi-symmetric Navier-Stokes equation. The pressure change inside a train have been calculated using first order difference approximation based on a linear equation between the pressure change ratio inside a train and the pressure difference of inside and outside of the train. The numerical results show that the pressure change inside the new Korean high-seed train passing through a tunnel of Seoul-Busan high-speed line at the speed of 330km/h satisfied well the Korean regulation for pressure change inside a passenger cabin if the train is satisfying the train specification for airtightness required by the regulation.

• Journal of Ocean Engineering and Technology
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• v.24 no.2
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• pp.47-52
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• 2010

The proper surface pressure on the pistons rings in the diesel engine of a ship is very important, because the pressure controls the oil that is needed to maintain friction at acceptable levels between the pistons and the cylinders. In this paper, basic and theoretical concepts to compute the ring pressure were formulated and applied to obtain the proper surface pressures on selected sample piston rings. During the calculation of the pressure on the piston rings, the computation of the accurate free shape of the piston ring was required. Earlier, Arnold and Prescott introduced theories to compute the free shapes of piston rings, and their approach used rectangular and polar coordinates. In this paper, the free shapes of piston rings using two different theories were computed and compared. The results were quite close, representing the free shape of the piston ring. Ring pressure was computed using the Arnold's free shape that was obtained. A simple GUI was made to compute the surface pressure on the piston rings.