• 제목/요약/키워드: Critical point

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초임계상태의 물에 대한 관 내 층류유동장 및 열전달계수 분포특성에 관한 연구 (A Study on the Laminar Flow Field and Heat Transfer Coefficient Distribution for Supercritical Water in a Tube)

  • 이상호
    • 설비공학논문집
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    • 제15권9호
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    • pp.768-778
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    • 2003
  • Numerical analysis has been carried out to investigate laminar convective heat transfer in a tube for supercritical water near the thermodynamic critical point. Fluid flow and heat transfer are strongly coupled due to large variations of thermodynamic and transport properties such as density, specific heat, viscosity, and thermal conductivity near the critical point. Heat transfer characteristics in the developing region of the tube show transition behavior between liquid-like and gas-like phases with a peak in heat transfer coefficient distribution near the pseudocritical point. The peak of the heat transfer coefficient depends on pressure and wall heat flux rather than inlet temperature and Reynolds number, Results of the modeling provide convective heat transfer characteristics including velocity vectors, temperature, and the properties as well as the heat transfer coefficient. The effect of proximity to the critical point is considered and a heat transfer correlation is suggested for the peak of Nusselt number in the tube.

CRITICAL POINTS AND WARPED PRODUCT METRICS

  • Hwang, Seung-Su;Chang, Jeong-Wook
    • 대한수학회보
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    • 제41권1호
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    • pp.117-123
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    • 2004
  • It has been conjectured that, on a compact orient able manifold M, a critical point of the total scalar curvature functional restricted the space of unit volume metrics of constant scalar curvature is Einstein. In this paper we show that if a manifold is a 3-dimensional warped product, then (M, g) cannot be a critical point unless it is isometric to the standard sphere.

THE EXISTENCE OF THE SOLUTION OF ELLIPTIC SYSTEM APPLYING TWO CRITICAL POINT THEOREM

  • Nam, Hyewon
    • 충청수학회지
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    • 제31권1호
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    • pp.53-64
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    • 2018
  • This paper deals with the study of solutions for the elliptic system with jumping nonlineartity and growth nonlinearity and Dirichlet boundary condition. We apply the two critical point theorem when proving the existence of nontrivial solutions for the elliptic system. We define the energy functional associated to the elliptic system and prove that the functional has two critical values.

A Study on the Abnormal Behavior of the Viscosity near the Critical Point

  • Kim, Won-Soo;Pak, Hyung-Suk;Chair, Tong-Seek
    • Bulletin of the Korean Chemical Society
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    • 제10권4호
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    • pp.372-374
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    • 1989
  • The new viscosity theory is applied to the abnormal behavior of the viscosity near the critical point. This theory suggests that the viscosity is equal to the product of the absolute pressure(kinetic pressure + internal pressure) and the collision time. We can find this abnormal behavior to be due to the large collision time near the critical point. The agreements between theoriticals and experimentals of the critical enhancement are satisfactory.

AC 저항측정법을 이용한 강자성 니켈의 큐리온도결정과 순도가 니켈의 임계현상에 미치는 영향 (The Study on the Purity Dependence of the Curie Point and the Critical Exponent of Ferromagnetic Nickel by the Measurements of AC Resistivity)

  • 양기원;이일수
    • 한국진공학회지
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    • 제5권2호
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    • pp.156-160
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    • 1996
  • The purity dependence of the Curie point and the critical exponent of heat capaicty has been studied by measuring the resistvity of nickel samples with several different purities. The resistivity was measured by the 4-point ac method with a lock-in amplifier. The Curie points determined from in-phase and out-of-phase signals were found to be consisten twith each other . We found that the Curie point and the critical exponent of heat capacity did not depend on the purity of samples.

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한계변형률 개념을 활용한 터널안전성 평가 (Tunnel Safety Assessment by using the Concept of the Critical Strain in the Ground)

  • 박시현;박성근
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2010년도 춘계 학술발표회
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    • pp.571-576
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    • 2010
  • In this study, an application method of critical strains concept for tunnels' safety by using the values of measured displacements which are obtained in the field is discussed. The aim is to: (1) study on the engineering meanings of critical strains concept by reviewing the previous researches and application examples with measured displacement values; (2) study on the engineering reasonability of critical strains concept with the view point of a tunnel engineering and a geotechnical engineering; (3) study on the features of ground deformation due to tunneling and reciprocal relation between total displacement and measured displacement; (4) evaluate a tunnel safety by using domestic measurements collected in the field; and (5) re-evaluate the control criteria which were previously used in the field, with the view point of critical strains concept. Consequently, it was confirmed that critical strains in the ground has a reasonability and a possibility of unified or common concept with the view point of a tunnel engineering.

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연고제(軟膏劑)의 경도(硬度)에 관한 연구(硏究)(IV) -온도(溫度)의 변화(變化)가 연고제(軟膏劑)의 대수경도(對數硬度) 미치는 영향(影響)- (The Study on the Hardness of Ointment(IV) -Influences of Temperature on the Apparent Logarithmic Hardness of Ointments-)

  • 이숙경
    • Journal of Pharmaceutical Investigation
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    • 제8권3호
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    • pp.24-31
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    • 1978
  • The relationship between temperature and apparent logarithmic hardness of ointments were clearly demonstrated. The followings were obtained as the results: 1. When the ointment base was mixed with additives and heated or cooled at various temperatures, the apparent logarithmic hardness in the first trend before reaching the critical point is subject to change mainly by the contents of the additive while in the secondary trend after reaching the critical point is subject to change mainly by the temperature. 2. No Change in the critical point was observed at different temperatures. It is assumed that the crittical point of such ointment bases has no relationship with temperatures and that the critical point itself should rather depend on the physicochemical properties of the additives.

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Fourier 변환을 이용한 ZnCdSe 전이점 연구 (Study on critical point of ZnCdSe by using Fourier analysis)

  • 윤재진;공태호;김영동
    • 한국진공학회지
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    • 제16권6호
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    • pp.458-462
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    • 2007
  • 타원편광분석법은 반도체 물질의 광 특성과 전이점 연구에 유용하게 쓰이는 기술이다. 측정된 유전율 함수로부터 전이점을 구하기 위해서 전통적으로 이차 미분스펙트럼을 이용하여 분석하는데, 이 방법은 high frequency 의 잡음을 크게 증폭시키는 단점이 있다. 본 연구에서는 역 공간 푸리에 변환 (Fourier transform)을 이용하여 low-, medium-, high-index 의 푸리에 계수로부터 baseline, 정보, high frequency 잡음을 분리하는 방법을 소개하고자 한다. 이 방법을 이용하여 광전자소자에 폭넓게 사용되는 ZnCdSe 화합물 반도체의 $E_1,\;E_1+{\Delta}_1$ 전이점에 대한 연구를 하여 전통적인 이차 미분법과 비교해 보았다.

THREE DIMENSIONAL CRITICAL POINT OF THE TOTAL SCALAR CURVATURE

  • Hwang, Seungsu
    • 대한수학회보
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    • 제50권3호
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    • pp.867-871
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    • 2013
  • It has been conjectured that, on a compact 3-dimensional orientable manifold, a critical point of the total scalar curvature restricted to the space of constant scalar curvature metrics of unit volume is Einstein. In this paper we prove this conjecture under a condition that ker $s^{\prime}^*_g{\neq}0$, which generalizes the previous partial results.

APPLICATIONS OF CRITICAL POINT THEOREMS TO NONLINEAR BEAM PROBLEMS

  • Choi, Q-Heung;Jin, Ying-Hua;Choi, Kyung-Pyo
    • 호남수학학술지
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    • 제29권1호
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    • pp.19-40
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    • 2007
  • Let L be the differential operator, Lu = $u_{tt}+u_{xxxx}$. We consider nonlinear beam equations, Lu + $bu^+$ = j, in H, where H is the Hilbert space spanned by eigenfunctions of L. We reveal the existence of multiple solutions of the nonlinear beam problems by critical point theorems.