• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.03a
• /
• pp.301-306
• /
• 2008

A pyrogen igniter was designed to satisfy the required condition of kick motor system for the space launch vehicle. We analyzed the ignition characteristics and performed the combustion tests to verify the internal ballistic performance. In the design process, the arc-image test was carried out to find the sufficient heat flux as varying the initial pressure from 10 to 700kPa. The analysis indicated that the initial pressure condition would delay ignition time within a range from 100 to 500ms. The combustion test with an inert chamber was also performed to understand the ignition characteristics with the variation of the initial pressure of free chamber volume. Finally, we confirmed that the igniter could provide the acceptable energy to ignite the propellant of kick motor at the ground test. The result of the ground tests showed that the ignition delay time was within the design range at the atmospheric pressure condition.

• Journal of the Korean GEO-environmental Society
• /
• v.12 no.11
• /
• pp.23-30
• /
• 2011

In this study, Terzaghi's formula was modified to solve problems considering the dilatancy effect of the soil for estimating the earth pressure acting on tunnel. It is performed for the comparison with Terzaghi's formula and modified Terzaghi's formula, tunnel model test result of Kobe University Rock Mechanics Laboratory. From comparison results of the earth pressure acting on tunnel, the earth pressure calculated by the Terzaghi's formula was estimated largest value. The earth pressure measured through the tunnel model test was least value. The difference between the earth pressure derived from Terzaghi's original formula and that derived from the modified formula was caused by the dilation effect, which was caused by the soil volume change. The difference between the earth pressure derived from the modified formula and the earth pressure measured through the tunnel model test, earth pressure results from the energy making failure surface. The results of FEM analysis were almost consistent with the results of mathematical analysis.

• 제어로봇시스템학회:학술대회논문집
• /
• 1991.10a
• /
• pp.974-978
• /
• 1991

Electro-pneumatic valve is an electro-mechanical device which converts electric signal into pneumatic flow mu or pressure. A measurement of dynamic response time is very important to evaluate valve performance. Dynamic response time of electro-pneumatic valve has a variation accordance with valve types, operating way and test standard. In this study, automatic measurement system of dynamic response time is composed based on test condition of dynamic response time test standard(CETOP, JIS). Also, in this study test pressure variation characteristics accordance with variation of solenoid excitation power, and we developed dynamic response measurement system enable to compare of and analyze these two characteristics.

• Wind and Structures
• /
• v.6 no.2
• /
• pp.91-106
• /
• 2003

The paper presents the results of 1:50 geometrical scale laboratory modeling of wind-induced point pressure on the roof of the Texas Tech University (TTU) test building. The nominal (prevalent at the TTU site) wind and two bounding (low and high turbulence) flows were simulated in a boundary-layer wind tunnel at Colorado State University. The results showed significant increase in the pressure peak and standard deviation with an increase in the flow turbulence. It was concluded that the roof mid-plane pressure sensitivity to the turbulence intensity was the cause of the previously reported field-laboratory mismatch of the fluctuating pressure, for wind normal and $30^{\circ}$-off normal to the building ridge. In addition, it was concluded that the cornering wind mismatch in the roof corner/edge regions could not be solely attributed to the wind-azimuth-independent discrepancy between the turbulence intensity of the approach field and laboratory flows.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.18 no.1
• /
• pp.8-13
• /
• 2010

Many vehicles have significantly under-inflated tires, primarily because drivers infrequently check their vehicles' tire pressure. When a tire is used while significantly under-inflated, its sidewalls flex more and the tire temperature increases, increasing stress and the risk of failure. In this study we evaluated tire safety and economical efficiency at various inflation pressure. For tire safety we performed FMVSS indoor durability test, measurement of rolling tire temperature, braking performance at dry/wet road condition, and rolling resistance test for economical efficiency. Results show that low pressure decreases tire durability of both speed-increase condition and load-increase condition. Heat temperature of rolling tire increases as pressure decreases and significantly under-inflated tires cause increase of vehicle's stopping distance at wet road condition. Also Under-inflation increases the rolling resistance of a tire and, correspondingly, decreases vehicle's fuel economy.

• Korean Journal of Clinical Laboratory Science
• /
• v.43 no.4
• /
• pp.138-144
• /
• 2011

Exaggerated blood pressure response during exercise has been found to increase the risk of future hypertension, left ventricular hypertrophy, cerebrovascular stroke, and CVD (cardiovascular disease) death. The aim of this study was to evaluate exercise capacity, cardiovascular factors in exaggerated blood pressure response during treadmill exercise testing. For research subjects, 72 subjects (normal blood response: 49 subjects, exaggerated blood response: 23 subjects) who received treadmill exercise test at J General Hospital were selected in this study. Exaggerated SBP (systolic blood pressure) response was defined as an SBP of 210 mmHg or greater during a maximal treadmill exercise test. The group with an exaggerated SBP response showed significantly higher values for RPP (rate pressure product) compared with the group with a normal SBP response. Subjects with METs (metabolic equivalents) had lower exaggerated SBP response than normal SBP response group. Subjects with recovery SBP had delayed exaggerated SBP response than normal SBP response group. Exaggerated SBP response to exercise is negative correlation with METs.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.15 no.2
• /
• pp.109-115
• /
• 2003

The performance of two vertical-blade eliminators (V1, V2) and two horizontal-blade ones (H1, H2) for absorption chillers were tested in terms of pressure drop and refrigerant entrainment. The test was carried out using a wind tunnel with a cross section of 300 mm$\times$300 mm. The pressure drop of four eliminators tested was found to be in the rage of 1.0~2.7mm $H_2O$ at the face velocity of 2m/s. In the refrigerant entrainment test the vertical-blade eliminators showed much better performance than the horizontal-blade ones. The horizontal-blade eliminators showed satisfactory results at the air velocity of 2m/s but exceeded the limit value at 3 m/s. Since the cooling capacity of a machine is lowered by about 2.5% at the pressure drop of 1 m $H_2O$, more researches are required to reduce the pressure drop in the eliminator.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2001.03a
• /
• pp.551-558
• /
• 2001

The horizontal drain method is one of methods improving reclamation ground. This method reduces consolidation time by using drained installed horizontally, and negative pressure is applied on end of these drains by vacuum pump. But, effective negative pressure still wasn't evaluated in applying this method to reclamation ground. To estimate optimum negative pressure, soil box test that make a model the in-situ by installing horizontal drains in the center is performed pressing different vacuum pressure In the laboratory, and the variations in settlement and volume of drained water through the drains during consolidation process were measured. Also, water content with distance from drain and with depth is measured after the test.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2001.03a
• /
• pp.411-418
• /
• 2001

The last 30 years have been significant worldwide growth in the use of EPS as a lightweight fill material. This paper analyzes the compressible inclusion function of EPS which can results in reduction of static earth pressure by accomodating the movement of retained soil. A series of model tests was conducted to evaluate the reduction of static earth pressure using EPS inclusion and determine the optimum stiffness of EPS, Also, field test was conducted to evaluate the reduction of static earth pressure using EPS inclusion. Based on field test it is found that the magnitude of static earth pressure was reduced about 20% compared with theoretical active earth pressure.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.4 no.3
• /
• pp.10-21
• /
• 1996

In this study, as a strategy to improve shift characteristics, the authors developed a new style pressure modulator which can reduce shock torque during power shift by modulating the pattern of pressure increase in the cylinder for actuating the clutch. The remarkable merits of this new pressure modulator lie in its structural simplicity and durability, because the modulator is only composed of a poppet type valve and a few orifices. The usefulness of the new pressure modulator is confirmed by experiments and numerical analyses on a clutch control hydraulic system simplified for easy test. Also, the excellency of the transmission with the new pressure modulator is verified by experiments on a test bench for simulating the running power train of an excavator.