• Title/Summary/Keyword: Three phase boundary

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Three phase flow simulations using the fractional flow based approach with general initial and boundary conditions

  • Suk, Heejun
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2004.04a
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    • pp.88-91
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    • 2004
  • The multiphase flow simulator, MPS, is developed based on the fractional flow approach considering tile fully three phase flow with general initial and boundary condition. Most existing fractional flow-based models are limited to two-phase flow and specific boundary conditions. Although there appears a number of three-phase flow models, they were mostly developed using pressure based approaches. As a result, these models require cumbersome variable-switch techniques to deal with phase appearance and disappearance. The use of fractional flow based approach in MPS makes it unnecessary to use variable-switch to handle the change of phase configurations. Also most existing fractional flow based models consider only specific boundary conditions. However, the present model considers general boundary conditions of most possible and plausible cases which consists of ten cases.

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Analysis of the Phase Current Measurement Boundary of Three Shunt Sensing PWM Inverters and an Expansion Method

  • Cho, Byung-Geuk;Ha, Jung-Ik;Sul, Seung-Ki
    • Journal of Power Electronics
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    • v.13 no.2
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    • pp.232-242
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    • 2013
  • To obtain phase currents information in AC drives, shunt sensing technology is known to show great performance in cost-effectiveness and therefore it is widely used in low cost applications. However, shunt sensing methods are unable to acquire phase currents in certain operation conditions. This paper deals with the derivation of the boundary conditions for phase current reconstruction in three-shunt sensing inverters and proposes a voltage injection method to expand the measurable areas. As the boundary conditions are deeply dependent on the switching patterns, they are typically analyzed on the voltage vector plane for space vector pulse width modulation (SVPWM) and discontinuous pulse width modulation (DPWM). In the proposed method, the voltage injection and its compensation are conducted within one sampling period. This guarantees fast current reconstruction and the injected voltage is decided so as to minimize the current ripple. In addition to the voltage injection method, a sampling point shifting method is also introduced to improve the boundary conditions. Simulation and experimental results are presented to verify the boundary condition derivation and the effectiveness of the proposed voltage injection method.

Impedance Properties of LSMC-YSZ Composite Cathode (LSMC-YSZ Composite 양극의 임피던스 특성)

  • 김재동;김구대;문지웅;김창은;이동아
    • Journal of the Korean Ceramic Society
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    • v.35 no.9
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    • pp.917-922
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    • 1998
  • The polarization characteristics of the cathodes were discussed which were composed YSZ and ${(La_{0.75 }Sr_{0.25 })}_{0.95}Mn_{0.8 }Co_{0.2}O_3$ The three-phase-boundary length increased with the addition of YSN resulting in the minimum po-larization resistance at 60(LSMC) : 40(YSZ) wt% When LSMC-YSZ compoiste cathodes was sintered at $1200^{\circ}C$ minimum polarization resistance was observed and the capacitace increased with increasing sintering tem-perature.

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Investigation of the Voltage Collapse Mechanism in Three-Phase PWM Rectifiers

  • Ren, Chunguang;Li, Huipeng;Yang, Yu;Han, Xiaoqing;Wang, Peng
    • Journal of Power Electronics
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    • v.17 no.5
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    • pp.1268-1277
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    • 2017
  • Three-phase pulse width modulation (PWM) rectifiers are usually designed under the assumption of ideal ac power supply and input inductance. However, non-ideal circuit parameters may lead to a voltage collapse of PWM rectifiers. This paper investigates the mechanism of voltage collapse in three-phase PWM rectifiers. An analytical stability boundary expression is derived by analyzing the equilibrium point of the averaging state space model, which can not only accurately locate the voltage collapse boundary in the circuit parameter domain, but also reveal the essential characteristic of the voltage collapse. Results are obtained and compared with those of the trial-error method and the Jacobian method. Based on the analysis results, the system parameters can be divided into two categories. One of these categories affects the critical point, and other affects only the instability process. Furthermore, an effective control strategy is proposed to prevent a vulnerable system from being driven into the instability region. The analysis results are verified by the experiments.

COMPARISON OF NUMERICAL METHODS FOR TERNARY FLUID FLOWS: IMMERSED BOUNDARY, LEVEL-SET, AND PHASE-FIELD METHODS

  • LEE, SEUNGGYU;JEONG, DARAE;CHOI, YONGHO;KIM, JUNSEOK
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.20 no.1
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    • pp.83-106
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    • 2016
  • This paper reviews and compares three different methods for modeling incompressible and immiscible ternary fluid flows: the immersed boundary, level set, and phase-field methods. The immersed boundary method represents the moving interface by tracking the Lagrangian particles. In the level set method, an interface is defined implicitly by using the signed distance function, and its evolution is governed by a transport equation. In the phase-field method, the advective Cahn-Hilliard equation is used as the evolution equation, and its order parameter also implicitly defines an interface. Each method has its merits and demerits. We perform the several simulations under different conditions to examine the merits and demerits of each method. Based on the results, we determine the most suitable method depending on the specific modeling needs of different situations.

Effects of α2/β Volume Fraction on the Superplastic Deformation (2 상 Ti3Al-xNb 계 금속간 화합물들의 초소성 특성에 미치는 상분율의 영향)

  • 김지식
    • Transactions of Materials Processing
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    • v.11 no.5
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    • pp.447-456
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    • 2002
  • A study has been made to investigate the boundary sliding and its accommodation mode with respect to the variation of $\alpha$$_2$/$eta$ volume fraction during superplastic deformation of two-phase Ti$_3$Al-xNb intermetallics. Step strain rate and load relaxation tests have been performed at 950, 970 and 99$0^{\circ}C$ to obtain the flow stress curves and to analyze the deformation characteristics by the theory of inelastic deformation. The results show that the grain matrix deformation and boundary sliding of the three intermetallics containing 21, 50 and 77% in $eta$ volume fractions are well described by the plastic deformation and viscous flow equations. Due to the equal accommodation of both $a^2$ and $\beta$ phases, the accommodation modes for fine-grained materials are in good agreement with the iso-strain rate models. The sliding resistance analyzed for the different boundaries is the lowest in the $\alpha$$_2$/$\alpha$$_2$ boundary, and increases in the order of $\alpha$$_2$/$\alpha$$_2$<< $\alpha$$_2$/$\beta$ = $\beta$/$\beta$, which plays an important role in controlling the superplasticity of the alloys with the various $\alpha$$_2$/$\beta$ phase ratio.

Morphology and Segregation of Sulfide Inclusions in Cast Steels (II) (Influence of [Mn/S] Ratios on the Morphology of Sulfide Inclusions in Fe-Mn-S Alloys) (주강의 유화물 형태와 편석에 대한 연구 (II) (Fe-Mn-S 합금의 유화물 형태에 미치는 Mn/S비의 영향))

  • Park, Heung-Il;Kim, Ji-Tae;Kim, Woo-Yeol
    • Journal of Korea Foundry Society
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    • v.29 no.6
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    • pp.270-276
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    • 2009
  • After casting button-type small ingots of ternary Fe-Mn-S alloys which had three different Mn/S ratios (1, 5 and 70) in a vacuum arc furnace, the effect of the ratio on the sulfide formation was investigated. In case of the Mn/S ratio of 1, if alloy composition was located in an iron-rich corner on a Fe-Mn-S ternary phase diagram, only duplex MnS-FeS sulfide films were observed in the grain boundary. If the alloy composition was located in the miscibility gap area of the phase diagram, primary globular dendritic sulfides and dendritic sulfide slags were generated within the grain and tubular monotectic sulfides were also detected in the grain boundary. When the Mn/S ratio was 5, if the alloy composition was in the iron-rich corner, only bead-like sulfides were generated. On the other hand, if the composition was in the miscibility gap area, globular dendritic sulfides and dendritic sulfide slags were generated in the form of primary sulfide inclusions and rod-like eutectic sulfides were observed in the grain boundary. Especially, if the contents of Mn and S increased more in the miscibility gap area of the phase diagram, primary globular sulfides containing iron intrusions were observed. In case of Mn/S ratio of 70, if the contents of Mn and S was decreased in the Fe corner of the phase diagram, only bead-like sulfides were observed in the grain boundary. Despite the composition was outside the miscibility gap area of the phase diagram, if the contents of Mn and S increased, clusters of fine sulfide particles as well as fine spherical primary monophase sulfides were observed in the grain boundary.

The Effect of particle size and ratio of LSM-YSZ powders on SOFC cathod properties (LSM과 YSZ의 분말크기 및 분말크기비가 SOFC의 양극특성에 미치는 영향)

  • 김재동;김구대;박지애
    • Journal of the Korean Ceramic Society
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    • v.37 no.3
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    • pp.227-232
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    • 2000
  • The LSM-YSZ composite electrode as a mixture of LSM and YSZ shows percolation characteristics. It was identified that the polarization resistance of LSM-YSZ composite electrode depend on YSZ connectivity by changing powder size ratio of the DLSM/DYSZ. That is, YSZ in composite electrode showed low electrochemical activity without YSZ connectivity. However, the polarization resistance decreased abruptly with YSZ connectivity due to high electrochemical activity of YSZ in composite electrode. Because the amount of three phase boundary is dependent on LSM and YSZ particle size, the polarization resistance of cathode decreases as LSM and YSZ particle size decreases.

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3-D information of Object by Modified Goldstein Algorithm at Digital holography

  • Yoon, Seon-Kyu;Kim, Sung-Kyu
    • 한국정보디스플레이학회:학술대회논문집
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    • 2007.08b
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    • pp.1486-1489
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    • 2007
  • Generally many kind of phase unwrapping method are used to obtain three-dimensional feature in digital holography. Goldstein algorithm is representative method. But Goldstein algorithm has some problems. We developed a modified Goldstein algorithm that could solve the problem of Goldstein algorithm using the boundary information. Obtained three-dimensional information can be applied to 3-D contents of stereoscopic, multi-view, SMV, or holographic display.

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Effect of rotation on Stoneley waves in orthotropic magneto-thermoelastic media

  • Parveen, Lata;Himanshi, Himanshi
    • Wind and Structures
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    • v.35 no.6
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    • pp.395-403
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    • 2022
  • The present research is concerned with the study of Stoneley wave propagation at the interface of two dissimilar homogeneous orthotropic magneto-thermoelastic solids with fractional order theory of type GN-III with three phase-lags and combined effect of hall current and rotation. With the help of appropriate boundary conditions the secular equations of Stoneley waves are obtained in the form of determinant. The characteristics of wave such as phase velocity, attenuation coefficient and specific loss are computed numerically. The effect of rotation on the Stoneley wave's phase velocity, attenuation coefficient, specific loss, displacement components, stress components and temperature change has been depicted graphically. Some particular cases are also derived in this problem.