• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.471-477
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• 1998

A constant flow-rate control valve provides effective distributions and controls of running water in a pipe system. The noise characteristics were measured to reveal the noise sources depending on pressure differences across a valve. Valve noise is mostly dominated by bubble dynamics under cavitating conditions. In this study, the sound powers from a flow control valve of constant flow rates are effectively normalized. Flow-excited dynamic systems for which there is no strong coupling between the flow and the system response can be described using a linear source-filter model. On this assumption, the normalized sound powers can be decomposed of noise source function and a response function. The source spectra in, terms of cavitation frequency show cavitation events occurring at narrow banded frequencies greater than 10 kHz. There also possibly exist two kinds of cavitating modes based on our experimental data.

• 한국방재학회 논문집
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• 제10권1호
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• pp.103-109
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• 2010

본 연구에서는 자유수면 흐름에 적용할 수 있는 연직방향에 대해 좌표변환된 3차원 동수압 모형을 제시하였다. 제시한 모형은 자유수면과 동수압의 해석을 위하여, 2중 예측-수정(double predictor-corrector)방법을 적용하였다. 본 연구에서는 정확한 동역학적 경계조건(자유수면에서의 압력은 0인 조건)을 적용하는 방법을 검토하였고, 제시한 모형을 이용한 수치모의 결과를 해석해와 비교하여 본 연구에서 제시한 모형의 우수성을 검증하였다.

• Wind and Structures
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• 제18권6호
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• pp.651-668
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• 2014

Wind tunnel tests are conducted to investigate the wind loads on vertical fixed-roof cylindrical tanks with a very low aspect ratio of 0.275, which is a typical ratio for practical tanks with a volume of $100,000m^3$. Both the flat-roof tank and the dome-roof tank are investigated in present study. The first four moments of the measured wind pressure, including the mean and normalized deviation pressure, kurtosis and skewness of the pressure signal, are obtained to study the feature of the wind loads. It is shown that the wind loads are closely related to the behavior of flow around the structure. For either tank, the mean wind pressures on the cylinder are positive on the windward area and negative on the sides and the wake area, and the mean wind pressures on the whole roof are negative. The roof configurations have no considerable influence on the mean pressure distributions of cylindrical wall in general. Highly non-Gaussian feature is found in either tank. Conditional sampling technique, envelope method, and the proper orthogonal decomposition (POD) analysis are employed to investigate the characteristics of wind loads on the cylinder in more detail. It is shown that the patterns of wind pressure obtained from conditional sampling are similar to the mean pressure patterns.An instantaneous pressure coefficient can present a wide range from the maximum value to the minimum value. The quasi-steady assumption is not valid for structures considered in this paper according to the POD analysis.

• Journal of Chest Surgery
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• 제19권1호
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• pp.68-74
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• 1986

15 patients with constrictive pericarditis who underwent interphrenic pericardiectomy from January, 1981 to April, 1983 and 11 patients who underwent radical pericardiectomy from May, 1983 to September, 1984 were compared to the clinical improvement and the results of pre- and postoperative cardiac catheterization. In the group of partial pericardiectomy the pericardium was removed anteriorly from the left phrenic nerve to the right phrenic nerve and in the group of radical pericardiectomy the pericardium was removed from almost entire surface of the heart including diaphragmatic surface and posterior wall of the left ventricle. The following results were obtained. 1. Both group of the patients showed marked symptomatic improvement early after operation. 2. The central venous pressure was decreased significantly after operation in both group of the patients. 3. The right atrial mean pressure and pulmonary arterial mean pressure decreased significantly after operation in both group of the patients and there was no significant difference in the amplitude of decrease between the two groups. 4. The right ventricular end-diastolic pressure and left ventricular end-diastolic pressure were decreased postoperatively in both group of the patients and the patients of the radical pericardiectomy showed more decrease than the patients of interphrenic pericardiectomy, and in the group of radical pericardiectomy the right and left ventricular end-diastolic pressure were normalized postoperatively but in the group of partial pericardiectomy they showed abnormally high pressure persistently. 5. The ejection fraction showed normal level pre- and postoperatively in both group of the patients.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.730-739
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• 2010

Stress history increases in penetration resistance due to the increase in residual horizontal stress of granular soil. This study analyzes the effect of stress history on the results of CPT and DMT from calibration chamber specimen in OC as well as NC state. Test results show that the normalized cone resistance by mean effective stress correlates well with the relative density and the state parameter, whereas the normalized cone resistance with regard to vertical effective stress is a little affected by stress history. The horizontal stress index($K_D$) in DMT more reflects the influence of stress history on granular soil than the dilatometer modulus($E_D$) and cone resistance($q_c$). The $K_D/K_0$, in which the effect of stress history on $K_D$ is compensated by the at-rest coefficient of earth pressure, $K_0$, is related to relative density, state parameter and the normalized cone resistance by mean effective stress. It is also observed that the normalized dilatometer modulus by mean effective stress($E_D/{\sigma_m}'$) is unique correlated with the state parameter, regardless of stress history.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1571-1580
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• 2008

Subsea tunnels that link land to island and among nations for transportation, efficient development of limited surface and pursuit of economic development should be designed to support pore water pressure on the lining. It is generally constructed in the bed rock of the sea bottom. When the tunnel excavation face meets fractured-zones below sea bottom, collapse may occur due to an increase of pore water pressure and large inflow. Such an example can be found in the Norwegian subsea tunnel experiences in 1980's. In this study hydraulic behavior of tunnel heading is investigated using numerical method based on the collapse of Norwegian subsea tunnel. The effect of pore water pressure and inflow rate were mainly concerned. Horse-shoe shaped model tunnel which has 50 m depth from the sea bottom is considered. To evaluate hydraulic performance, parametric study was carried out for varying relative permeability. It is revealed that pore water pressure has increased with an increase of sea depth. Especially, at the fractured-zone, pore water pressure on the lining has increased significantly. Inflow rate into tunnel has also increased correspondingly with an increase in sea depth. S-shaped characteristic relation between relative permeability and normalized pore water pressure was obtained.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1923-1929
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• 2003

The present study investigated the microcirculation of blood in the left common artery (LCCA). In order to develop a mathematical model for microcirculation in LCCA, the present study adopted preexisted set of measured morphological data on anatomy, mechanical properties of the coronary vessels, viscosity of blood, the basic laws of physics, and the appropriate boundary conditions. In this study, the statistical distribution of blood pressure, blood flow, and blood volume in the LCCA were determined based on the anatomical branching pattern of the coronary arterial tree and the statistical data of blood vessel dimensions. Our calculations were in good agreement with the previous studies. The present results showed that the mean longitudinal pressure drop profile was function of the vessel order numbers. It was found that the normalized pressure drop was a logarithmic function of the compliance.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.17-23
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• 2004

A cylindrical constant volume combustion bomb is used to investigate the combustion characteristics and to analyze the heat quantity of homogeneous charge methane-air mixture under various initial pressures, excess air ratios and ignition times. As the overall pressure increase, the values of maximum combustion pressure, maximum heat release rate and cumulative heat release have been increased. But it is not very meaningful to compare with some values such as maximum combustion pressure, maximum heat release rate and cumulative heat release for different overall pressure due to the different heat energy of supplied fuel. So the each value is needed to be compared with normalized value, which is divided by the entered fuel energy. To analyze the heat quantity, some definitions including the CHR ratio, the UHC ratio and the HL ratio are needed and are calculated. As the overall pressure increase, the CHR ratios and the UHC ratios have been decreased, while the HL ratios have been increased. The CHR ratio of 300 ms has the higher value than that of 10000ms, and the HL ratios of 300 ms have a lower value.

• 대한기계학회논문집A
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• 제26권6호
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• pp.1099-1106
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• 2002

This paper provides engineering J-integral and crack opening displacement (COD) estimation equations for circumferential through-wall cracked pipes under internal pressure and under combined internal pressure and bending. Based on selected 3-D finite element calculations for the circumferential through-wall cracked pipes under internal pressure using the idealized power law materials, the elastic and plastic influence functions for fully plastic J-integral and COD solutions are found as a function of the normalized crack length and the mean radius-to-thickness ratio. These developed GE/EPRI-type solutions are then re-formulated based on the enhanced reference stress method. Such re-formulation not only provides simpler equations for J-integral and COD estimations, but also can be easily extended to combined internal pressure and bending. The proposed equations are compared with elastic-plastic finite element results using actual stress-strain data, which shows overall excellent agreement.

• 대한기계학회논문집B
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• 제26권5호
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• pp.750-756
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• 2002

The effect of equivalence ratio and velocity on the stability of flame in dump combustor was studied in an atmospheric pressure, laboratory scathe dump combustor operating natural gas. Traditionally, peak-to-peak pressure, fluctuation of the heat release rate and Rayleigh index were used to find and control the combustion instability. Cross correlation coefficients, Ci,j which is defined as the normalized value of the integration of the product of two of the mixer pressure, dump plane pressure and heat release rate, are introduced to see whether the flame is stable or not. Ci,j shows more sensitive to combustion status than Rayleigh index in steadily burning flame. Also, the result indicates that the amplitude of Ci,j between heat release and mixer pressure goes up before the flame at the rich de-stabilizing equivalence ratio near $\psi$=0.85. t means Ci:j at this case has a potential to detect the de-stablizing moment in prior to becoming unstable in dump combustor.