• 한국안전학회지
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• 제8권4호
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• pp.114-119
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• 1993

The explosion characteristics of nonhomogeneous LPG-Air mixtures was measured in a cylindrical vessel and a pipe. The maximum explosion pressure, the maximum rate of explosion pressure rise, and the flame propagation velocity were measured and compared with that of homogeneous explosion by changing the effective factors on the explosion of nonhomogeneous mixtures such as pressure difference, effusion time and delay time. Explosion was occured even in the lower concentration than the lean flammability limit of mixture. The maximum explosion pressure was increased with increase of LPG concentration, however, the maximum explosion pressure rise was not in the nonhomogeneous explosion. An d the flame propagation velocity was decreased with nonhomogeneity, however, the maximum explosion pressure was always above 0.7kg/$\textrm{cm}^2$.

• 한국전문물리치료학회지
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• 제21권1호
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• pp.37-46
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• 2014

Asymmetric sitting posture may cause asymmetric buttock pressure and unilateral low back pain (LBP). The purpose of this study was to compare the differences of buttock pressure between both sides, and pelvic angle (sagittal and coronal planes) during typing in a sitting position on a pressure mat (Baltube) in individuals with and without unilateral LBP. Ten subjects with unilateral LBP and ten subjects without unilateral LBP were recruited for this study. Buttock pressure was measured using a pressure mat and pelvic angles were measured using a palpation meter. The subjects performed typing in a sitting posture for 30 minutes. Pressure data were collected and averaged at initial term (from start to first minutes) and final term (last minutes of 30 minutes). Angles of pelvic tilting were measured after 30 minutes typing. Pressure asymmetry values (difference in pressure between both sides) were calculated at the initial and final terms. A two-way analysis of variance was used to compare the differences between the initial and final pressure asymmetry values in subjects with and without unilateral LBP. An independent t-test was applied to compare the pelvic tilt angles between the two groups. To compare the change of pressure from the initial term to the final term between the symptomatic and asymptomatic sides in the unilateral LBP group, a paired t-test was applied. In the unilateral LBP group, the pressure asymmetric value at the final term was significantly greater than that of the initial term (p<.05). The angle of pelvic tilting in coronal plane was significantly greater in the unilateral back pain group compared to the without unilateral LBP group (p<.05), however, there was no significant difference in the angle of pelvic tilting in the sagittal plane between the two groups (p>.05). In the unilateral LBP group, the change of pressure from the initial term to the final term was significantly less in the symptomatic side (-6.90 mmHg) than the asymptomatic side (5.10 mmHg). This asymmetric sitting posture may contribute to unilateral LBP in the sitting position. Further studies are needed to determine if asymmetric weight bearing in sitting causes unilateral LBP or if unilateral back pain causes asymmetric weight bearing, and if the correction of asymmetric weight bearing in sitting can reduce unilateral LBP.

• 대한간호학회지
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• 제19권3호
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• pp.285-298
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• 1989

This study investigated the effect of changing position from supine to standing upright on the circulation of young men and women. Healthy men and women ranging from age of 18 to 24 were examined. Two minutes before standing, the baseline heart rate and blood pressure were measured. Heart rate and blood pressure were recorded immediately and at every minute for 10 minutes after standing upright. Differences in heart rate and blood pressure between supine and standing upright position were evaluated. The results were summarized as follows : 1. Heart rate increased significantly immediately and at every minute for 10 minutes after standing upright. 2. Systolic blood pressure increased significantly immediately and at every minute for 4 minutes after standing upright. 3. Diastolic and mean blood pressure increased significantly immediately and at every minute for 10 minutes after standing upright. 4. Pulse pressure immediately and at every minute for 10 minutes after standing upright was significantly narrower than that of supine position. 5. There was no significant difference of heart rate between men and women after standing upright. 6. Systolic and diastolic blood pressure of men after standing upright was significantly greater than those of women. From these results, it may be concluded that heart rate, systolic, diastolic and mean blood pressure and pulse pressure increase after standing upright, and systolic and diastolic blood pressure in men is greater than those of women after standing upright.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1122-1127
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• 2004

an isolated droplet combustion exposed to pressure perturbations in stagnant gaseous environment is numerically conducted. Governing equations are solved for flow parameters at gas and liquid phases separately and thermodynamic parameters at the interfacial boundary are matched for problem closure. For high-pressure effects, vapor-liquid interfacial thermodynamics is rigorously treated. A series of parametric calculations in terms of mean pressure level and wave frequencies are carried out employing a n-pentane droplet in stagnant gaseous air. Results show that the operating pressure and driving frequency have an important role in determining the amplitude and phase lag of a combustion response. Mass evaporation rate responding to pressure waves is amplified with increase in pressure due to substantial reduction in latent heat of vaporization. Phase difference between pressure and evaporation rate decreases due to the reduced thermal inertia at high pressure. In addition to this, augmentation of perturbation frequency also enhances amplification of vaporization rate because the time period for the pressure oscillation is much smaller than the liquid thermal inertia time. The phase of evaporation rate shifts backward due to the elevated thermal inertia at high acoustic frequency.

• Journal of Advanced Marine Engineering and Technology
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• 제31권6호
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• pp.687-693
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• 2007

It has been known that one of the main obstacles of improving the performance of positive displacement hydraulic turbine is pressure pulsation which occurs at the regions upstream and downstream of the turbine. In order to suppress the pressure pulsation. occurrence reason of the pressure pulsation should be understood in detail Therefore. this study aims to establish a CFD analysis method by which the phenomena of unsteady pressure pulsation can be examined with high accuracy. Internal flow field of the turbine is modeled simply to generalize the relation between the pressure pulsation and internal flow. The results show that the Present CFD method adopting unsteady calculation can be applied successfully to the analysis of the Phenomena of Pressure Pulsation. Occurrence of the Pressure pulsation is due to the difference of the rotational speed of turbine rotors When driving rotor rotates by uniform speed and fellowing rotor rotates by variable speed, very large Pressure pulsation occurs within the turbine periodically.

• 한국임상수의학회지
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• 제33권6호
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• pp.321-324
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• 2016

The present study compared two indirect blood pressure methods at thoracic limb, pelvic limb, and coccygeal sites. For measurement of blood pressure, 48 client-owned dogs in a clinical setting were used. When comparing the results obtained by doppler and oscillometric methods, there were significant differences in blood pressure of the thoracic and pelvic limbs. The Doppler machine produced significantly higher blood pressure value than oscillometry measured at thoracic and pelvic limbs. The difference in blood pressure between the two methods was not significant when measured in the tail. Comparison of blood pressure measured at three different sites by doppler, blood pressure measured at pelvic limb was higher than at thoracic limb and tail. In case of oscillometry, there were no significant differences between the three sites. The results of this study indicate that mechanical and positional differences were existed in blood pressure measurements at the canine thoracic limb, pelvic limb and tail.

• 한국해양공학회지
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• 제26권6호
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• pp.66-73
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• 2012

A pressure compensated chamber of a pilot mining robot isolates and protects an electrical-electronic system from the ambient highly pressured water. Since the inner pressure of the chamber is compensated with outer water pressure using hydraulic oil and pressure compensator, there exists a pressure difference, less than 1 bar, between outer and inner surface. The structural safety of the chamber is obtained relatively easier than the canister type which inner pressure is kept as the atmospheric pressure. However, due to the adoption of box shape for space efficiency and usage of the transparent engineering plastic viewport for checking inner circumstance, the viewport can be largely deformed. This large deformation can cause an additional tensile force, called the prying force, to the bolt-flange connection parts of the viewport. In this paper, we suggest the structural design equation considering the prying action for designing the structure of a box-shape pressure compensated chamber.

• 상하수도학회지
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• 제20권2호
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• pp.197-206
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• 2006

The leakage in the water distribution system means both the loss of money and water resource. To minimize the leakage, we introduced the pressure control method using the pressure reducing valve and pump schedule. For the pressure control, the total leakage is needed to divide into each node. In this study, EPANET 2.0 was used to simulate the water networks in two selected blocks after the total leakage was distributed with each node by four ways. The leakage was allocated into each node as water measured by meter, water pressure, water faucets and Lpcd and simulated by EPANET 2.0. Regardless of the leakage distribution ways, there was no significant difference between the measured water and the estimated water pressure. Thus, the leakage distribution way using water pressures estimated by simulation could be recommended. The scenarios controlling the pressure reducing valve and pump were made in two blocks(A and B). $86,713m^3/year$ leakage in the A block and $11,442m^3/year$ in the B block could be reduced as controlling the pressure reducing valve and pump schedule. It was shown that the fifty million won a year can be saved in the A block and 6.8 million won in the B block.

• ALGAE
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• 제21권2호
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• pp.245-251
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• 2006

Diurnal and age-related changes in air pressure were measured in air bladders of Ascophyllum nodosum from the Atlantic coast of Nova Scotia. Exterior and interior bladder volumes vary significantly with 4 and 6 y bladders being about 40% larger than 2 y bladders (p < 0.01). Freshly collected bladders yielded a mean pressure of 40.8 ± 6.5 cm H2O. Overnight (20 h) dark treatment at 15°C generated pressure reductions by 80% in 2 y bladders but only by about 30% in 4 and 6 y bladders. Furthermore, in 2 y bladders 8 out of 11 bladders were reduced to atmospheric pressure. Pressure losses were inversely related to pressure recovery after 2.5 h in natural daylight, but after 5 h in daylight there was no significant difference in pressure within the age groups. Even under 25% of full illumination, bladders inflated to full pressure after 5 h. The results show that differences in bladder age and bladder wall thickness have roles in diurnal patterns of bladder inflation and deflation. These results confirm that bladder inflation is based on photosynthetic O2 production and not on partial pressures of O2 in the surrounding medium as was suggested for Sargassum. Chemical analyses of fluid recovered after the interior of bladders were washed with saline showed no evidence for the occurrence of surfactant that might be responsible for maintaining the air-liquid interface.

• 한국추진공학회지
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• 제18권1호
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• pp.58-64
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• 2014

다양한 홀 크기를 갖는 오리피스를 이용하여 1, 2단 챔버를 구성하는 공압 모사모터를 제작하였다. 오리피스의 면적과 노즐 목 면적비에 따라 2단 챔버 작동 시 1단 챔버와 압력차가 발생한다. 이 압력차는 실제 추진기관 성능에 영향을 미치므로 오리피스 면적 및 설계에 대한 고찰이 필요하다. 2단 챔버 작동 시 1단 챔버 압력은 오리피스 크기 및 1단 챔버 형상에 따른 와류형성으로 에너지 손실이 발생한다. 본 논문에서는 상용 CFD(Computational Fluid Dynamics) 프로그램(ANSYS FLUENT V14.5)를 이용하여 유동을 모사하였다.