• Title, Summary, Keyword: 분극저항

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Forward probing utilizing electrical resistivity and induced polarization for predicting mixed-ground ahead of TBM tunnel face (전기비저항과 유도분극을 활용한 TBM 터널 굴착면 전방 복합지반 예측 기법)

  • Ryu, Jinwoo;Park, Jinho;Lee, Seong-Won;Lee, In-Mo;Kim, Byung-Kyu
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.1
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    • pp.55-72
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    • 2018
  • A method that can predict the mixed-ground condition ahead of a TBM tunnel face during tunnel construction utilizing electrical resistivity and induced polarization (IP) was proposed in this study. Effect of TBM advancement approaching the mixed-ground condition (composed of soil layer overlying rock layer) when currently running through soil zone on the electrical resistivity and IP measuring was assessed with laboratory-scale experiments. The resistivity and IP values were measured using four electrodes, by installing two electrodes on the tunnel face (at the cutterhead), and the other two electrodes on the segment lining. The test results showed that both of the measured resistivity and IP values were kept increasing as the TBM is approaching the soil-rock mixed-ground. Also, to get the more reliable results for predicting the mixed-ground condition, it was recommended that the measurement is made at the tunnel face utilizing 4-electrodes installed at the cutterhead as well as it is made utilizing the 2-electrodes installed at the segment lining along with the 2-electrodes installed on the tunnel face (at the cutterhead) so that two measured results are compared each other.

Surface Smoothening Effects of a Matrix Retaining Electrolyte on Characteristics of a PAFC (PAFC용 전해질 매트릭스의 표면 평탄화 처리가 전지 특성에 미치는 영향)

  • Yun, Gi-Hyeon;Hong, Seong-Ha;Jang, Jae-Hyeok;Kim, Chang-Su
    • Korean Journal of Materials Research
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    • v.7 no.12
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    • pp.1097-1104
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    • 1997
  • 인산형 연료전지(PAFC)용 전해질 매트릭스의 표면 거칠기를 감소시켜 분극저항을 줄이고 작업성을 향상시키기 위해 SiC whisker를 사용하여 일반적인 테이프 캐스팅법으로 제조된 매트릭스의 거친 표면을 평탄화 처리하였다. 구형 입자의 분무공정을 이용하여 표면 평탄화 처리(process l)하는 경우와 롤링을 이용하여 표면 평탄화 처리(process 2)하는 두가지 공정을시도하였으며, 두가지 공정 모두 기공율과 인산 함침도를 유지시키면서, 매트릭스의 표면 거칠기를 감소시키고 기공압, 가소성 및 인장강도를 향상시킬 수 있었다. 위와 같이 제조한 매트릭스로 연료전지를 구성하여 교류 임피던스 분석을 한 결과, 표면 평탄화 처리는 매트릭스 표면의 거칠기를 감소시킴으로써 전극과의 접촉시 계면에서의 분극 저항을 감소시켜 전지성능을 향상시키는 것으로 나타났다. process 2는 표면의 거칠기 감소뿐 아니라 표면에서의 인산함침도가 커서 가장 우수한 전지특성을 나타내었으며, process 1은 매트릭스 표면에 불규칙하게 존재하는 거대 기공을 완전히 제거하고 기공압을 크게 향상시킬 수 있기 때문에 대형의 매트릭스 제조를 가능하게 하였다.

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H-Polarized Scattering by a Resistive Strip Grating with Zero Resistivity at Strip-Edges Over a Grounded Dielectric Plane (접지된 유전체 평면위의 스트립 양끝에서 0 저항율을 갖는 저항띠 격자구조에 의한 H-분극 산란)

  • Yoon, Uei-Joong
    • The Journal of Advanced Navigation Technology
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    • v.15 no.3
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    • pp.349-354
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    • 2011
  • In this paper, H-polarized scattering problems by a resistive strip grating with zero resistivity at strip-edges over a grounded dielectric plane according to the strip width and grating period, the relative permittivity and thickness of a dielectric layer, and incident angles of a transverse electric (TE) plane wave are analyzed by applying the Fourier-Galerkin Moment Method (FGMM). The tapered resistivity of resistive strips has zero resistivity at strip edges, then the induced surface current density on the resistive strip is expanded in a series of Chebyshev polynomials of the second kind as a orthogonal ploynomials. The sharp variations of the reflected power are due to resonance effects were previously called wood's anomallies, the numerical results for the reflected power are compared with those of uniform resistivity in the existing papers.

A Study on the Crevice Corrosion Behavior of Chromium Plating (크롬도금의 틈부식 거동에 관한 연구)

  • 곽남인;임우조
    • Journal of the Korean institute of surface engineering
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    • v.36 no.4
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    • pp.324-328
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    • 2003
  • This study was made on the crevice corrosion behavior of chromium plating in fresh water. Under the various crevice, the electrochemical polarization test of chromium plating was carried out. Results are discussed In terms of corrosion potential, polarization resistance, corrosion current density and cathodic control of chromium plating.

E-Polarized Reflection Coefficient by a Tapered Resistive Strip Grating with Zero Resistivity at Strip-Edges (저항띠의 양 끝에서 0으로 변하는 저항률을 갖는 주기격자에 의한 E-분극 반사계수)

  • 윤의중;양승인
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.19 no.2
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    • pp.331-337
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    • 1994
  • The scatting problem by E-polarized plane wave with obique incidence on a tapered resistive strip grating with zero resistivity(perfectly conducting) at strip-edges is analyzed by the method of moments in the spectral domain. Then the induced surface current density on the strip is expanded in a series of Chebyshev polynomials of the second kind. The expasion coefficients are calculated numerically in the spectral domain, the numerical results of the geometric-optical reflection coefficient for the tapered resistivity in this paper are compared with those for the existing uniform resistivity. And the position of sharp variation points in the magnitude of the geometric-optical reflection coefficient can be moved by varying the incident angle and the strip spacing, It is found out that these sparp variation points are due to the transition of higher mode between the propagation mode and the evanescent mode.

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H-Polarized Scattering by a Resistive Strip Grating with the Tapered Resistivity Over a Grounded Dielectric Plane : from Finite at One Strip-Edge to Zero at the Other Strip-Edge (접지된 유전체 평면위의 변하는 저항율을 갖는 저항띠 격자구조에 의한 H-분극 산란 : 한쪽 모서리에서 유한하고 다른쪽 모서리로 가면서 0인 경우)

  • Yoon, Uei-Joong
    • The Journal of Advanced Navigation Technology
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    • v.15 no.4
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    • pp.543-548
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    • 2011
  • In this paper, H-polarized electromagnetic scattering problems by a resistive strip grating over a grounded dielectric plane according to the strip width and grating period, the relative permittivity and thickness of a dielectric layer, and incident angles of a TE (transverse electric) plane wave are analyzed by applying the FGMM (Fourier-Galerkin Moment Method). The tapered resistivity of resistive strips in this paper varies from finite resistivity at one edge to zero resistivity at the other edge, then the induced surface current density on the resistive strip is expanded in a series of Jacobi polynomials of the order ${\alpha}=1$, ${\beta}=0$ as a kind of orthogonal polynomials. The numerical results of the normalized reflected power show in good agreement with those of existing papers.

Modelling of the Resistance Model for Anode and Cathode for Molten Carbonate Fuel Cells (용융탄산염 연료전지용 공기극과 연료극의 저항 모델링)

  • LEE, CHANG-WHAN;JUNG, JUNG-YUL
    • Transactions of the Korean hydrogen and new energy society
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    • v.29 no.3
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    • pp.267-273
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    • 2018
  • From the experiments of various temperature and gas compositions, total resistance which is composed of ohmic resistance, anode resistance, cathode resistance and Nernst loss was calculated wit simple assumption. In this work, the anode and the cathode resistance was modelled with new equation which can account for the correlation between the operating temperature and the gas composition. The proposed model can predict the resistance with maximum error of 2.57% and employed in the simulation of molten carbonate fuel cells.

Application of Spectral Induced Polarization Method for Skarn Metallic Deposits Exploration (스카른 금속광상 탐사를 위한 광대역 유도분극법 적용성)

  • Park, Samgyu;Shin, Seung Wook;Son, Jeong-Sul;Cho, Seong-Jun
    • Geophysics and Geophysical Exploration
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    • v.19 no.4
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    • pp.212-219
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    • 2016
  • The development of more advanced geophysical exploration techniques is necessary because the orebodies as yet discovered are increasingly changing in characteristics from shallow/high-grade to deep/low-grade. In this work, laboratory measurement of physical properties of rock samples and a field survey and interpretation of spectral induced polarization (SIP) have been conducted in a skarn metallic deposit, Gagok mine. The purpose of this study is that the applicability of SIP in the exploration of skarn metallic deposits is verified by the comprehensive interpretation between SIP characteristics of rocks obtained from the laboratory measurements and inverted survey results from the field data. In order to understand the SIP characteristics of each lithology, the data of eighty nine rock samples utilized in the previous studies were revaluated. The field survey was carried out using frequency of 0.25 Hz along a survey line designed for intersecting lithological boundaries and evaluating mineralized zones. The mineralized rocks were more conductive (low-resistivity) and capacitive (high-chargeability or strong-phase) than other rocks. Thus, SIP can be one of the very useful tools for the mineral exploration of the skarn deposits.

Domain formation and expansion during periodic poling of congruent $LiNbO_3$ using external field (조화용융조성 $LiNbO_3$의 주기적 분극 반전 동안 도메인 생성 및 이동에 관한 연구)

  • Kwon, S.W.;Yang, W.S.;Lee, H.M.;Kim, W.K.;Lee, H.Y.;Yoon, D.H.;Song, Y.S.
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.16 no.2
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    • pp.53-58
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    • 2006
  • When external field was applied to congruent $LiNbO_3$, it was investgated for domain formation and expansion of $LiNbO_3$. The domain wall velocities of 0.5 mm thickness $LiNbO_3$ were 28.70, 16.02 and $5.75{\mu}m/sec$ under poling field of 23.5, 22.0 and 21.0 kV/mm, respectively. As $1 M{\Omega}$ resistor was used in domain inversion system, harmonic domain inversion was not achieved by rapid domain expansion. And 50% duty cycle periodically poled $LiNbO_3$ have been fabricated by charge control using $10 M{\Omega}$ resistor.

Evaluation of Concentration Polarization at Feed in the Permeation of VOCs/$N_2$ mixtures through PDMS membrane (VOCs/질소 혼합물 증기투과시 공급액부 경계층에서의 농도분극 분석을 위한 모델식 확립)

  • 염충균;이상학;최정환;이정민
    • Membrane Journal
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    • v.11 no.2
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    • pp.74-82
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    • 2001
  • By using a phenomenological approach, model equations incorporating the resistance-in¬series concept were established to evaluate quantitatively concentration polarization in the boundary layer in feed adjacent to the membrane surface in the vapor permeation and separation of volatile organic compounds (VOCS)/$N_2$ mixture through po]y(dimethylsiloxane) (PDMS) membrane. The vapor permeations of various VOCS/$N_2$ mixtures through PDMS membrane were carried out at various feed flow rates. Chlorinated hydrocarbons, such as, methylene chloride, chlorofonn, 1,2-clichloroethane and 1,1,2-trichloroethane were used as organic vapor. By fitting the model equations to the experimental penneation data. the model parameters were detennined. respectively. Both the mass transfer coefficient of VOC across tbe boundary layer and concentration polarization modulus as a measure of the extent of concentration polarization were eitimated Quantitatively by the mooe1 equations with the determined model parameters. From the analysis on the detennined model parameters, the boundary layer resistance due to the concentration polarization of VOCs component was found to be more significant when the condensability of voe was greater. This study seeks to emphasize the importance of the boundary resistance on the vapor penneation of the vapor/gas mixtures with high permeability and high selectivity towards the minor component VOC.

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