• 전기화학회지
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• 제11권4호
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• pp.227-241
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• 2008

This article involves a unified treatment of equilibrium thermodynamics of the chemical reaction coupled with other interfacial (phase boundary) reactions. The modified (restrictive) chemical potential ${\mu}_k^+$, such as electrochemical potential, hydrostatic-chemical (mechanochemical) potential (exceptionally in the presence of the pressure difference) and surface-chemical potential, was first introduced under the isothermal and isobaric conditions. This article then enlightened the equilibrium conditions in case where the release of chemical energy is counterbalanced by the supply of electrical energy, by the supply of hydrostatic work (exceptionally in the presence of ${\Delta}p$), and finally by the release of surface energy, respectively, at constant temperature T and pressure p in terms of the modified chemical potential ${\mu}_k^+$. Finally, this paper focussed on the difference between chemical and electrochemical equilibria based upon the fundamentals of the isothermal and isobaric equilibrium conditions described above.

• 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.

• 한국신뢰성학회지:신뢰성응용연구
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• 제12권3호
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• pp.165-176
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• 2012

Hydrostatic bearing improves performance and life time of a product by avoiding solid friction and reducing viscosity friction with the help of creating pressure equilibrium between two faces doing relative motion. This study suggests failure analysis and test evaluation for a ball joint that adopts the hydrostatic bearing and introduces the entire process to improve reliability of the product by design improvement. A typical failure is growth of friction torque by solid friction, and its failure cause is determined and the improvement is proposed. Finally, reliability improvement is established by analysis of the results of before and after acceleration test.

• 한국CDE학회논문집
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• 제21권1호
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• pp.90-98
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• 2016

When ships and offshore plants are flooded or the floating crane is equipped with a heavy object, these floating structures are excessively inclined. In this case, immersion, heel, and trim affecting the hydrostatic restoration performance are very large and are coupled each other. In this paper, in order to calculate a static equilibrium position of floating structures with excessive inclination, the nonlinear governing equations were constructed by sequential linearization. In the governing equation, the immersion, heel, and trim are fully coupled, and the equations are represented using a plane area, a primary moment, and a moment of inertia of the water plane area. Therefore, it is possible to calculate the additional factor related the water plane area for estimating stability. Position and orientation of the floating structure are obtained by iterative calculation. The calculated results are compared with the previous studies in the aspect to the performance and the accuracy.

• 한국항해항만학회지
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• 제43권5호
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• pp.328-334
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• 2019

Underwater architecture in providing a comfortable living space underwater is mandated to survive prevailing environmental loads, especially hydrostatic ambient water pressure exerted on the structure of individual habitat hulls at depth and hydrodynamic fluctuation of external forces that perturb the postural equilibrium and mooring stability of the underwater housing system, for which the design including the hull shape and mooring system constraint the responses. In this study, the postural stability of a proposed underwater floating housing system with three vertically connected ellipsoidal-shape habitat hulls of different sizes are theorized and calculated for hydrostatic stability, using MATLAB in the volumetric integration of a hull and the weight of operational loads under assumed scenarios. The assumptions made in the numerical method to estimate the stability of the habitat system include the fixed weight of the hulls, and their adjustable loads within operational limits for the set meteorological oceanic conditions. The purpose of this study was to numerically manipulate a) The buoyancy and b) The adjusted center of mass of the system within the range of designed external and internal load changes, by which the effective mooring system capability and postural equilibrium requirements were argued with the quantitative analysis.

• 천문학회보
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• 제3권
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• pp.18-23
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• 1978

The evolutionary tracks of a protostar of one solar mass under quasi-hydrostatic equilibrium are computed with mass-accretion time scales of $10^3,\;10^4,\;10^5\;and\;10^6$ years, and their resulting behaviors in the H-R diagram are discussed. It is found that there exists a critical time scale of mass accretion, which reverses the course of their evolutionary tracks. A value of the critical time scale appears to lie between $10^3\;and\;10^4$ years. The physical cause for the presence of the critical time scale is discussed. Finally, it is proposed that star formation requires at least several $10^3$ years before any star is born out of dark dense interstellar clouds.

• 한국해양공학회지
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• 제28권6호
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• pp.527-532
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• 2014

The thickness of Arctic sea ice is a particularly significant factor in Arctic shipping and other ice-related research areas such as scientific sea ice investigations and Arctic engineering. In this study, the relation between the measured sea ice thickness and freeboard on the Chukchi and Beaufort Seas during the 2010 and 2011 Arctic cruise of the icebreaking research vessel "Araon" were considered. An assumption of hydrostatic equilibrium was used to estimate the ice thickness as a function of the freeboard. Then, to examine the degree of error, a sensitivity analysis of the thickness estimation of the sea ice was conducted. The error in the density and depth of the snow and the error in the density of the seawater were subordinate parameters, but the density of the ice and the freeboard were the primary parameters in the error calculation. The presented relation formula showed fairly close agreement between the calculated and measured results at a freeboard of >0.24 m.

• 천문학회보
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• 제35권2호
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• pp.74.1-74.1
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• 2010

Using two-dimensional numerical hydrodynamic simulations, we investigate the regulation of star ormation rates in turbulent, multiphase, galactic gaseous disks. Our simulation domain is xisymmetric, and local in the radial direction and global in the vertical direction. Our models nclude galactic rotation, vertical stratification, self-gravity, heating and cooling, and thermal onduction. Turbulence in our models is driven by momentum feedback from supernova events ccurring in localized dense regions formed by thermal and gravitational instabilities. Self-onsistent radiative heating, representing enhanced/reduced FUV photons from the star formation, s also taken into account. Evolution of our model disks is highly dynamic, but reaches a quasi-teady state. The disks are overall in effective hydrostatic equilibrium with the midplane thermal ressure set by the vertical gravity. The star formation rate is found to be proportional pproximately linearly to the midplane thermal pressure. These results are in good agreement with the predictions of a recent theory by Ostriker, McKee, and Leroy (2010) for the thermal/dynamic equilibrium model of star formation regulation.

• 대한기계학회논문집
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• 제5권2호
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• pp.122-130
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• 1981

Equation of equilibrium is derived and solved for an infinite isotropic solid under applied hydrostatic stress which is uniform at large distance, and disturbed by a spherical precipitate which has isotropoc elastic constants dirrerent form those of the matrix. A linear strain hardening behavior of the matrix is assumed, and an elasto-plastic sloution is obtained. The difference of the total strain energy stored inthe infinite solid with and without a precipitate is computed, and compared with that for purely elastic case. Finally the effect of the ratio of the bulk modulus of the precipitate to that of the matrix and the effct of linear strain hardening rate on the plastic zone size and the energy difference are discussed.

• 소성∙가공
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• 제9권6호
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• pp.590-597
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• 2000

A finite element formulation lot the simulation of axisymmetric sheet hydroforming is proposed, and an implicit program is coded. In order to describe normal anisotropy of steel sheet, Hill's non-quadratic yield function (Hill, 1979) is employed. Frictional contacts among sheet surface, rigid tool surface, and flexible hydrostatic pressure are considered using mesh normal vectors based on finite element of the sheet. Applied hydraulic pressure is also considered as a function of forming rate and time and treated as an external loading. The complete set of the governing relations comprising equilibrium and interfacial equations is approximately linearized for Newton-Raphson algorithm. In order to verify the validity of the developed finite element formulation, the axisymmetric bulge test is simulated. Simulation results are compared with other FEM results and experimental measurements and showed good agreements. In axisymmetric hydroforming processes of a disk cover, formability changes are observed according to the hydraulic pressure curve changes.