• Journal of the Korean Institute of Gas
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• v.7 no.3 s.20
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• pp.58-64
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• 2003

This paper presents design safety analysis of pressure vessels. The gas pressure and thermal loads are applied to the pressure vessel simultaneously. In this study, ASME Sec. VIII Div. 2 code was accepted for the safety design of high-pressure vessel. And this result was analyzed using a coupled thermal-mechanical FEM analysis technique. The FEM computed result shows that ASME design code may not guarantee for combined loads of high gas pressure and thermal loads. And solid pressure vessel may be safe compared to other pressure vessels with supporting rings round the cylinder body.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.4
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• pp.703-707
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• 2007

The line pressure control system for an automotive transmission in which a bleed type variable force solenoid(VFS) is applied, has been constructed and experimentally investigated. The hydraulic circuit of the system includes a line pressure control valve, a reducing valve, an accumulator, various orifices and a VFS. Static and dynamic responses of the throttle and line pressure have been monitored and discussed for various test conditions.

• Journal of the Korean Applied Science and Technology
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• v.35 no.3
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• pp.948-955
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• 2018

The purpose of this study was to compare plantar pressure and COP parameters in three types of arch support insole during stair descent in elderly with flatfoot. A total of 14 women elderly were recruited for this study. Pedar-X was used to obtain plantar pressure(peak pressure, mean pressure, and contact area) and COP(distance, displacement, excursion) parameters. One-way ANOVAs were used to compare peak pressure, mean pressure, and contact area, distance of COP, displacement of COP, and excursion of COP. Among the plantar pressure parameters, significant(p<0.05) differences were observed in M3 for the peak pressure, M2, M3, and M4 for the mean pressure, and M2, M3, and M6 for the contact area. Among the COP parameters, distances of COP both in the mediolateral and anteroposterior axes revealed significant(p<0.05) differences. The larger peak pressure values of type A and B insoles were observed as compared to normal insole. The larger peak pressure and shorter COP distance values of type A and B insoles were observed as compared to normal insole.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.4
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• pp.392-398
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• 2009

Theoretical thrust equations for the diverse nozzle expansion condition were derived. By using the obtained thrust equations, parametric studies were carried out to estimate the effect of pressure exponent, minimum operation pressure, ambient pressure and extinguishment pressure on thrust modulation performance in pintle-nozzle solid rocket motors. Analysis results showed that thrust turndown ratio can be easily attained by small nozzle-throat area variation at high pressure exponent, low minimum operation pressure, high ambient pressure and high extinguishment pressure condition. At those conditions, the highest chamber pressure to obtain the intended thrust turndown ratio can be minimized.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.2
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• pp.1-9
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• 1999

Applicability of the pressure gradient method which is formulated based on pressure gradient is verified against turbulent flow analysis. In the pressure gradient method, pressure gradient instead of pressure itself is obtained using continuity constraint. Since correct pressure gradient is found only when mass conservation is satisfied, pressure gradient method can reflect physics of flow field properly The pressure gradient method is formulated with semi-staggered grid system which locates each primitive variables on the same grid point but evaluates pressure gradient in-between. This grid system ensures easy programming and reflection of correct physics in analysis. For verifying applicability of this method, the pressure gradient method is applied to turbulent flow analysis with low Reynolds number $\kappa$-$\varepsilon$ model. Turbulent flows include fully developed channel flow, backward-facing step flow, and conical diffuser flow. Prediction results show that the pressure gradient method can be applied to turbulent flow analysis. However, the pressure gradient method requires somewhat long computation time. Proper way to find optimum under-relaxation factor, $\gamma$, is also need to be developed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.288-292
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• 2008

Dome shape design method of filament wound (FW) composite pressure vessel, which can create various dome shape with fixed boss opening, was suggested. And, the performance indices (PV/W) for composite pressure vessel with same boss opening but different dome shape were investigated by finite element analysis (FEA) and hydro-test. The FEA showed good agreement with test results for burst pressure. Generally, as the dome shape of pressure vessel was changed to flat dome, the inner volume is increased and the burst pressure is decreased. In the case of above ${\rho}_o$=0.54, the performance index showed decreased value due to the low burst pressure. However, at ${\rho}_o$=0.35, the dome shape change brings not significant reduction of burst pressure and performance index.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.748-751
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• 2010

To launch rocket on launch pad, propellants and gases are charged into the rocket by remote control system. Using pneumatic pressure-reducing regulators, kinds of gases with various pressure levels are supplied into launch pad. As most of operations for launching the vehicle are remotely controled in the launch control room, pressure pulsations due to rapidly gas supply at the upstream of regulators can make the required operating pressure range missed and cause damage to the regulators. In this paper, the optimum design methods of pressure regulators of pressure-reducing system on launch pad using high-pressure gases were investigated to solve the aforementioned problems and for stable gas supply to launch pad.

• The Journal of the Korea Contents Association
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• v.15 no.1
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• pp.462-474
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• 2015

This article is aimed to investigate the role of social pressure in the influential relationship of user motivation on user commitment in social media. On this purpose, user motivation in social media was divided into 3 sub-dimensions as social motivation, functional motivation and hedonic motivation and social pressure was also categorized into informational isolation pressure and conformity pressure and then it was explored that how the social pressure makes differential effects in the relationship of each dimensions of user motivation and user commitment. Major findings are as follows. First, user's social motivation and hedonic motivation in social media had significant positive influence on user commitment. Second, the informational isolation pressure showed moderating effect in the relation of functional motivation and commitment. Third, conformity pressure displayed moderating effect in the relation of social motivation and commitment. This article suggests empirical supports about the role of social pressure in the phenomena of social media use and commitment, but requires to explore more specific factors and multi-dimensional studies in regard of social pressure in social media.

• Membrane Journal
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• v.13 no.1
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• pp.20-28
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• 2003

In this study, we try to formularize simultaneous equations to make a prediction about pressure drop for designing intravascular artificial lung assist device. Designing parameters to predict the effect of pressure drop and designed modules under various conditions were studied through an experimental modeling before inserting the artificial lung assist device into as venous. We measured pressure drop in various number of hollow fiber membranes, when the inside diameter of shell is fixed in 3 cm, and tried to develope the prediction equations by curve fitting based on the correlation between the experimental pressure drop and the device frontal area or packing density. The results showed that pressure drop increased with 2nd order functional formula as the liquid flow rate, the frontal area, and the packing density increased. Also, we can estimate the pressure drop as a function of the frontal area or packing density. The pressure drop obtained from the experiment was similar to that from the equation, confirming the usefulness of the equation.

• Explosives and Blasting
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• v.35 no.1
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• pp.1-17
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• 2017

The understanding of the pressure associated with air blast, which travels through air, and its effect on surface and underground structures is highly important. It is necessary to determine the pressure change with time and distance for a computer simulation of the explosion impact on a structure. From the previous studies, many empirical equations for estimating the parameters related to the pressure change. In this study, the empirical equations for predicting peak overpressure, duration of positive phase, impulse, minimum negative pressure, duration of negative pressure, arrival time, and decay constant were reviewed and analyzed. Also, the pressure changes predicted from the Kingery equation, which is the most commonly used, and from the other empirical equations were compared.