• Journal of the Korean Society for Precision Engineering
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• v.26 no.4
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• pp.55-63
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• 2009

This paper reports on the theoretical and experimental study of the pressure ripples in a pressure unbalanced type vane pump which have widespread use in industry. Because they can infinitely vary the volume of the fluid pumped in the system by a control. Pressure ripples occur due to the flow ripples induced by geometry of side plate, leakage flow, reverse flow from the outlet volume produced by pressure difference between pumping chamber and outlet volume when the pumping chamber connected with the outlet volume. In this paper, we measured the pressure variation of a pumping chamber, reaction force on a cam ring, the mathematical model for analyzing the pressure ripples which included vane detachment and fluid inertia effects in notch area has been presented, and was applied to predict the level and the wave form of the pressure ripples according to operating conditions.

• Journal of Korean Foot and Ankle Society
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• v.12 no.1
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• pp.41-46
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• 2008

Purpose: This study was designed to evaluate characteristics of foot pressure distribution with or without partial prosthetic foot in transmetatarsal amputee. Materials and Methods: The subjects were 9 transmetatarsal amputees. Foot pressures were measured at hallux, the $1^{st}-5^{th}$ metatarsal head (MTH), mid-foot, condyle area by F-scan system in amputated or contralateral foot during active walking. Results: In amputated foot, mean peak pressure was greatest in midfoot without prosthetic foot but it was greatest in hindfoot with prosthetic foot. In unaffected foot, although mean peak pressure was higher in hallux, and $1-5^{th}$ MTH compared to amputated foot, it was greatest in hind foot both with and without prosthetic foot. However, in unaffected foot, mean peak pressure significantly decreased in hallux and $5^{th}$ MTH after wearing the prosthetic foot. There was a significant difference in mean peak pressure in hallux and $5^{th}$ MTH between amputated and unaffected foot after wearing prosthetic foot. However, other region had no significant difference with or without prosthetic foot between feet. Conclusions: The use of partial prosthetic foot tends to shift weight bearing from the heel area to forefoot and could significantly reduce hind foot peak pressure and redistributed to peak pressure. The partial prosthetic foot can also offer the peak pressure to reduction both amputated foot and unaffected foot and help to toe off during walking.

• Biomedical Engineering Letters
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• v.8 no.4
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• pp.399-404
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• 2018

The purpose of this study was to evaluate the accuracy of a mobile wireless digital automatic blood pressure monitor for clinical use and mobile health (mHealth). In this study, a manual sphygmomanometer and a digital blood pressure monitor were tested in 100 participants in a repetitive and sequential manner to measure blood pressure. The guidelines for measurement used the Korea Food & Drug Administration protocol, which reflects international standards, such as the American National Standard Institution/Association for the Advancement of Medical Instrumentation SP 10: 1992 and the British Hypertension Society protocol. Measurements were generally consistent across observers according to the measured mean ${\pm}SD$, which ranged in $0.1{\pm}2.6mmHg$ for systolic blood pressure (SBP) and $0.5{\pm}2.2mmHg$ for diastolic blood pressure (DBP). For the device and the observer, the difference in average blood pressure (mean${\pm}$SD) was $2.3{\pm}4.7mmHg$ for SBP and $2.0{\pm}4.2mmHg$ for DBP. The SBP and DBP measured in this study showed accurate measurements that satisfied all criteria, including an average difference that did not exceed 5 mmHg and a standard deviation that did not exceed 8 mmHg. The mobile wireless digital blood pressure monitor has the potential for clinical use and managing one's own health.

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

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.6
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• pp.823-831
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• 1998

In order to investigate the impulsive noise at the exit of high-speed railway tunnel and the pressure transients inside the tunnel, numerical calculations using a Total Variation Dimishing difference scheme were applied to axisymmetric unsteady compressible flow field. Some compression wave forms were assumed to model the compression wave produced in real high-speed railway tunnel. The numerical data were extensively explored to analyze the peak over-pressure and maximum pressure gradient in the pressure wavefront. The effect of the distance and cross-sectional area ratio between two-continuous ducts on the characteristics of the pressure waves were investigated. The peak over-pressure inside the second duct decreases for the distance and cross-sectional area ratio between two tunnels to increase. The peak over-pressure and maximum pressure gradient of the pressure wavefront inside the second duct increase as the maximum pressure gradient of initial compression wave increases. The present results were qualitatively well agreed with the results of the previous shock tube experiment.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.80-85
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• 2003

In the present paper, dynamics analyses of pressure control characteristics have been performed in a variable pressure solenoid valve. A number of solenoid valves have been used in the electronic control system, especially automatic transmission of an automobile. Variable pressure solenoid valve is intended to produce spatial movement by the electrical signal. Dynamics analyses of pressure control characteristics have been practiced by the Finite Difference Method, which show the pressure distribution in the solenoid valve. The results of numerical analyses show the dependence of pressure distribution on the displacement of the spool in the solenoid valve, and then, are compared with the experimental results.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.228-233
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• 2014

Reduction of the atmospheric pressure in high altitude affects brake booster system which was operated by the difference between the intake pressure and the atmospheric pressure. So, braking system can not stably perform due to decrease of brake boost pressure. In this study, effects of altitude change on engine intake pressure was analyzed by prediction model of engine intake pressure which was studied previously. And engine intake pressure was simulated by simulation model in various driving conditions and environmental conditions.

• Journal of Korean Academy of Nursing
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• v.25 no.2
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• pp.341-350
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• 1995

A quasi-experimental study was conducted to examine the effect of ice pack application to post cardiac surgery toddlers before C-tube removal. Twenty toddlers aged 13 months to 24 months, who were admitted to the hospital for open heart surgery during the period from July, 1993 to October, 1993 were randomly assigned to the experimental or control group. An ice pack was applied to the C-tube insertion site for 8 minutes before C-tube removal for the experimental group. The children were videotaped during the procedure to assess pain behavior and crying time. The score on the Modified Behavioral Pain Scale(MBPS), crying time, and vital signs were measured to determine the effect of ice pack application. The data were analyzed using Mann-Whitney U test, Paired t-test, and Pearson correlation coefficient. The result of the study are as follows : 1. There was a significant difference between the experimental group and the control group in pain behavior (U=17.0, p=.01). 2. There was no significant difference between the two groups in crying time. 3. There was a significant difference between the two groups in heart rate (U=24.5, p=.05). 4. There was a significant difference between the two groups in systolic blood pressure (U=24.0, p=.05) 5. There was a significant difference between the two groups in diastolic blood pressure (U=23.0, p=.04). 6. There was no significant difference between the two groups in respiration rate. 7. Pain behavior was significantly correlated with heart rate, systolic blood pressure, and crying time (r=.50, .54 and .59, p<.05). The result showed that the ice pack application was effective to reduce pain related to C-tube removal for the toddlers. From the study, it is recommended that the effectiveness of the cold ap-plication to children undergoing different painful procedures be examined to determine the most effective length of cold application to reduce pain in children.

• Proceedings of the KSR Conference
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• 1999.05a
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• pp.83-94
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• 1999

This study is about design of vehicle for air tightness to pressure waves of high speed train. When the train runs to high speed over 300km/h, the comfort of passenger come down due to difference pressure between inside and outside of passenger room. The car-body was carried out the design of air-tightness, and the analysis of inside pressure of vehicle in tunnel by TG_TUN of ALSTOM Co. The result of analysis should be used the design of air pressurized system and car-body of G7 high speed train project.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.1 s.244
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• pp.1-7
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• 2006

The characteristics of micro gaseous flows in microchannels have been analyzed in view of flow resistance using the direct simulation Monte Carlo (DSMC) method which is a molecule-based numerical modeling technique. For this purpose, a DSMC code where the pressure boundary condition was specified at the inlet and outlet, has been developed and the results of simulations showed satisfactory agreements with the analytic solution in the slip flow regime. (0.01 < Kn < 0.1) By varying the height and length of the microchannel, the effect of pressure difference between the inlet and outlet was examined. The present computation indicates that the curvature in pressure distribution along the channel increases due to the effect of compressibility when the pressure difference increases. To obtain the flow resistance regardless of the channel dimensions, a standard curve is devised in the present study by introducing the concept of unit mass flowrate and unit driving pressure force. From this curve, it is shown that in micro flows, a significant deviation from the laminar incompressible flow occurs by reducing the flow resistance.