• 한국항공우주학회지
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• 제32권7호
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• pp.19-28
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• 2004

본 논문은 과도상태의 압력데이터로부터 평형상태의 압력을 예측하는 방법을 제시하고 있다. 압력을 측정하는 곳과 압력센서는 튜브로 연결되어져 있다. 측정하고자하는 압력 (측정압력)이 높은 경우에는 압력센서가 빠른 시간 내에 측정압력에 반응을 한다. 그러나 매우 낮은 압력을 측정하는 경우에는 압력센서가 실시간으로 측정압력에 반응을 하지 못하여 압력지연현상이 발생하게 된다. 이러한 압력지연현상을 파악하고자 여러 가지 실험이 수행되었다. 본 연구의 제시된 평형압력예측방법은 낮은 압력을 측정함에 있어서 측정시간을 단축시킬 수 있다.

• 천문학회지
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• 제12권1호
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• pp.1-5
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• 1979

The usual assumption of the pressure equilibrium between the convective elements and the surrounding fluid has been dropped, and the effects of the pressure perturbation of the convective element on its velocity and T perturbation have been estimated.

• 산업식품공학
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• 제15권3호
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• pp.214-220
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• 2011

중고압 하에서 $\beta$-glucosidase효소반응을 물리화학적 관점에서 연구하였다. 모델 기질 (p-nitrophenyl-${\beta}$-D-glucopyranoside)에 대한 $\beta$-glucosidase 효소의 작용에 대한 압력 효과를 실험 하였다. 즉, 압력 조건(25MPa, 50 MPa, 75 MPa, 100 MPa)과 시간 (10분, 60분, 1시간, 6시간, 24시간, 40시간)의 처리 조건에서 효소 활성도를 분광학적인 표준방법에 따라 측정하였다. 효소-기질 반응의 단계를 크게 kinetic 구간과 평형 구간으로 구분하여 물리화학적 모델을 적용하여, 정 역반응속도 상수, 평형상수, 압력에 의한 부피 감소 등을 산출하였다. 대기압에서 100MPa까지 압력이 증가할수록 효소-기질 반응의 생성물이 더 많이 형성되었으며 전형적인 kinetic 구간과 평형 구간이 나타났다. 압력, 시간, 생성물농도 등의 데이터로부터 kinetic 구간과 평형에서의 생성물 예측 모델을 완성하였다. 결론적으로 중고압 처리에 의하여 효소-기질 반응이 촉진됨을 알 수 있었고, 임의의 압력 및 시간 조건에 따른 생성물의 농도를 예측할 수 있게 되었다.

• 대한기계학회논문집
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• 제19권3호
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• pp.820-833
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• 1995

An analysis is performed to examine the equilibrium state and the stability of modeled Reynolds stress equations for homogeneous turbulent shear flows. The system of the governing equations consists of four coupled ordinary differential equations. The equilibrium states are found by the steady state solution of the governing equations. In order to investigate the stability of the system about its state in equilibrium, and eigenvalue problem is constructed. As a result, constraints for the coeffieients in the model equations are obtained by the stability condition of the equilibrium state as well as by their physically realizable bounds. It is observed that the models with pressure-strain rate correlation that are linear in the anisotropy tensor are stable and produce reasonable equilibrium tensor do not behave properly. Stability considerations about three most commonly used models are given in detail in the final section.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2001년도 제22회 KOSCI SYMPOSIUM 논문집
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• pp.106-118
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• 2001

A rigorous study of single droplet vaporization under quiescent high pressure atmosphere is attempted adopting method of flash evaporation calculation for vapor-liquid equilibrium. Results due to flash method shows excellent agreement with measurement. Also shown is the present model fairly capable of depicting transients of droplet vaporization under high pressure environment, such as ambient gas solubility, property variation, and multicomponent transports. Systematic treatment of these effects with emphasis on vapor-liquid phase equilibrium revealed; conventional treatment for subcritical droplet vaporization, such as $d^2$-law, leads to erroneous prediction of droplet history, augmented gas solubility is significant under supercritical pressure, and vaporization rate proportionally increase with pressure.

• 한국산업융합학회 논문집
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• 제7권1호
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• pp.97-105
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• 2004

The Vapor-liquid equilibrium data for the binary system of 2-methyl-2-propanol-2-butanone are measured at subatmospheric pressure of 100, 200, 300, 400, 500, 600, 700 and 760 torr. This study shows that the relations between logarithmic values of relative valatility(log ${\alpha}$)and liquid phase composition(${\chi}$) in the above binary systems are expressed as a linear function. When the linear relationships of between logarithmic values of relative volatilities and liquid phase compositions in the binary systems of various pressure intersect at a point, this empirical equation can be applied to the systems of this kind. From these relations the vapor-liquid equilibrium data are estimated and compared with the measured values to be in a good agreement with in accuracy ${\pm}0.0021$ for the various pressure.

• 드라이브 ㆍ 컨트롤
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• 제15권4호
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• pp.11-16
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• 2018

Pilot operated control valve for $CO_2$ refrigerant is a valve that can perform various functions according to the user's intention by replacing pilot units, widely used for flow rate, pressure, and temperature control of refrigeration and air conditioning systems. In addition, $CO_2$ refrigerant, that requires high pressure and low critical temperature, can be installed and used in all positions of the refrigeration system, regardless of high or low pressure. In this paper, response characteristics are modeled and analyzed based on behavior of the main piston of the pilot-operated control valve. Although various factors influence operation of the main piston, this paper analyzes the effect of equilibrium pressure depending on valve installation position and application, and inlet and outlet orifice size of the load pressure feedback chamber to determine feedback characteristics of the main piston. As a result, it was possible to quantitatively analyze the effect of change in equilibrium and load pressure feedback chamber flow path size on the change in main piston dynamic and static characteristics.

• 한국지반공학회지:지반
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• 제13권6호
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• pp.25-36
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• 1997

피에조콘을 이용하면 연약지반 개량후 임의의 시점에서 지반의 압밀도를 파악할 수가 있다. 이 경우 임의의 심도에서 피에조콘의 관입을 멈추고 간극수압이 일정한 값에 이를 때까지 간극 수압 소산시험을 실시하는데, 연약지반의 투수계수가 작기 때문에 대체적으로 상당히 오랜 시간 동안 소산시험을 하게 된다. 본 논문에서는 침하 분석기법 가운데 일반적으로 널리 알려져 있는 쌍곡선법, 아사오카법, 호시노법을 이용하여 간극수압 소산시험시의 평형간극수압을 각각 추정한 후 장시간에 걸친 실제 시험결과와 비교함으로써 간극수압 소산시험에 소요되는 시간을 단축할 수 있는 방법을 연구하였다. 그 결과, 호시노법을 이용한 추정방법이 가장 적합한 방법임을 알 수 있었으며 이를 이용한 효율적인 간극수압 소산시험 방법을 제시하였다.

• 한국생산제조학회지
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• 제21권3호
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• pp.401-407
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• 2012

The recent manufacturing process in the thin wafers and flat panel necessitate new approaches to reduce handling fragile and surface-sensitive damage of components. This paper presents a new pneumatic levitation for non-contact handling of parts and substrates. This levitation can achieve non-contact handling by blowing air into an air pressure pick-up head with radial passages to generate a negative pressure region. Negative pressure is caused by the radial air flow by nozzle throat and through holes connecting to the bottom region. The numerical analysis deals with the levitational motion with different design factors. The dynamic motion is examined in terms of force balance(dynamic equilibrium) occurring to the flow field between two objects. The stable equilibrium position and the safe separation distance are determined by analyzing the local pressure distribution in the fluid motion. They make considerable design factors consisting the air pressure pick-up head. As a result, in case that the safe separation distance is beyond 0.7mm, the proposed pick-up head can levitate stably at the equilibrium position. Furthermore, it can provide little effect of torque, and obtain more wide picking region according to the head size.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
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• pp.156-159
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• 2003

The analytic solution of displacements of thin cylindrical pressure vessel made by carbon fiber T700/Epoxy was obtained using equilibrium equations of orthogonal curvilinear coordinate system. Equilibrium equations with the assumed displacement field were derived from a reasonable description of the behavior of thin elastic shells using principle of virtual work. Some analyses of the theoretical solution are presented and compared with the results of hydraulic tests of the pressure vessel.