• Title, Summary, Keyword: conductivity

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Development of Conductivity Cell and Suppressor for Capillary Column Ion Chromatography (모세관 컬럼 이온 크로마토그래피를 위한 Conductivity Cell과 Suppressor의 개발)

  • Pyo, Dongjin;Kim, Hohyun
    • Analytical Science and Technology
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    • v.12 no.2
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    • pp.89-93
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    • 1999
  • In this study, conductivity cell and suppressor for micro-column ion chromatography were developed to analyze ions in small columns of samples. With a capillary column, the flow rate of the mobile phase is so small (usually $5{\sim}20{\mu}L/min$) that the usual conductivity cell can not be used. Therefore, we developed a new type of conductivity cell and suppressor which have small inner volumes. The conductivity cell was made with two Pt hypodermic needles (i.d. 0.010 mm) which are slightly separated (about $2{\mu}m$), and the suppressor was made of Nafion tubings. When several anions(fluoride, nitrite, nitrate, chlorate) were analyzed using developed conductivity cell and suppressor, a good chromatogram was obtained.

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Long-Term Hydraulic Conductivity and Cation Exchange of a Geosynthetic Clay Liner (GCL) Permeated with Inorganic Salt Solutions

  • Jo, Ho Young;Benson, Craig H.;Edil, Tuncer B.
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.59-62
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    • 2004
  • Hydraulic conductivity tests were conducted on a geosynthetic clay liner (GCL) for more than 2.5 yr using inorganic salt solutions to evaluate how the long-term hydraulic conductivity is affected by cation concentration and valence. Only small changes (i.e., $\leq$ 2X) in hydraulic conductivity (K) occurred during the test duration when the permeant solution was deionized (DI) water or 100 mM KCl and NaCl solutions. For weak CaCl$_2$ solutions ($\leq$ 20 mM), the hydraulic conductivities initially (< 0.2 yr) were comparable to the hydraulic conductivity obtained with DI water, but gradually increased by a factor of 2 to 13 over a period of nearly 2 yr. In contrast, the GCL permeated with strong CaCl$_2$ solutions ($\geq$ 50 mM) reached equilibrium nearly immediately, with a hydraulic conductivity approximately 2 orders of magnitude higher than the hydraulic conductivity to DI water.

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Electrical Conduction in $SrZr_{0.95}Y_{0.05}O_{2.975}$ Ceramics

  • Baek, Hyun-Deok;Noh, Jin-Hyo
    • The Korean Journal of Ceramics
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    • v.5 no.3
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    • pp.288-295
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    • 1999
  • Partial conductivities contributed by electron holes, oxygen ions, and protons were caluclated in $SrZr_{0.95}Y_{0.05}O_{2.975}$, using the reported formulae derived from the defect chemistry of HTPCs. Required parameters were obtained from the graphical analysis of total conductivity variation against partial pressure of water vapor and oxygen. Predicted overall conductivities showed a reasonable agreement with experimental measurements. The conductivity of the material showed a linear increase with square root of the water vapor pressure. This increase was due to proton conduction in an almost pure ionic conductivity. The calculation of partial conductivities at $800^{\circ}C$ resulted in an almost pure ionic conductivity at $P_{02}=10^{-10}$ atm and a predominant hole conductivity at $P_{02}=10^{-10}$ atm. Pure proton conduction was not expected at this temperature, contrary to the earlier reports. Discussions were made in relation with reported thermodynamic data and defect structure of the material. It was shown that from the total conductivity dependence on water vapor pressure, the pure ionic conductivity at low oxygen partial pressures could be separated into protonic and oxygen ionic conductivity in $ZrO_2$-based HTPCs.

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Effects of Sintering Conditions on the Electrical Conductivity of 1 wt% Y2O3-Doped AlN Ceramics (1 wt% Y2O3 첨가계 AlN 세라믹스의 소결 조건에 따른 전기전도도)

  • Lee, Won-Jin;Lee, Sung-Min;Shim, Kwang-Bo;Kim, Hyung-Tae
    • Journal of the Korean Ceramic Society
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    • v.44 no.2
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    • pp.116-123
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    • 2007
  • Electrical properties of AlN ceramics sintered with 1 wt% $Y_2O_3$ have been investigated. From the impedance spectroscopy, electrical conductivity of grain boundary was found to be much lower than that of grain. DC conductivity measurement showed the electrode polarization effects caused by blocking electrode. The heat-treatment at $1700^{\circ}C$ of the specimen sintered at $1850^{\circ}C$ transformed continuous pain boundary phases along triple boundary junctions into isolated particles in grain comers. The heat-treatment induced decreases both in grain and grain boundary conductivity, and in DC electrical conductivities. From the analysis on the transference number, ionic conductivity was shown to be more dominant than electron conductivity, which was due to ion compensation mechanism during oxygen incorporation into grain.

RF Conductivity Measurement of Conductive Zell Fabric

  • Nguyen, Tien Manh;Chung, Jae-Young
    • Journal of electromagnetic engineering and science
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    • v.16 no.1
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    • pp.24-28
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    • 2016
  • This study presents a conductivity measurement technique that is applicable at radio frequencies (RF). Of particular interest is the measurement of the RF conductivity of a flexible Zell fabric, which is often used to implement wearable antennas on clothes. First, the transmission coefficient is measured using a planar microstrip ring resonator, where the ring is made of a Zell fabric. Then, the fabric's conductivity is determined by comparing the measured transmission coefficient to a set of simulation data. Specifically, a MATLAB-based root-searching algorithm is used to find the minimum of an error function composed of measured and simulation data. Several error functions have been tested, and the results showed that an error function employing only the magnitude of the transmission coefficient was the best for determining the conductivity. The effectiveness of this technique is verified by the measurement of a known copper foil before characterizing the Zell fabric. The conductivity of the Zell fabric at 2 GHz appears to be within the order of $10^4S/m$, which is lower than the DC conductivity of $5{\times}10^5S/m$.

Fundamental Study of Deicing Pavement System Using Conductive Materials (전도성 재료를 사용한 도로결빙방지 포장시스템 개발을 위한 기초연구)

  • Lee, Kanghwi;Lee, Jaejun
    • International Journal of Highway Engineering
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    • v.17 no.5
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    • pp.11-18
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    • 2015
  • PURPOSES : The purpose of this study is to develop a deicing pavement system using carbon fiber or graphite with high electrical conductivity and thermal conductivity. METHODS: Based on literature reviews, in general, conventional concrete does not exhibit electrical and thermal conductivity. In order to achieve a new physical property, experiments were conducted by adding graphite and carbon fiber to a mortar specimen. RESULTS: The result of the laboratory experiment indicates that the addition of graphite can significantly reduce the compressive strength and improve the thermal conductivity of concrete. In the case of carbon fiber, however, the compressive strength of the concrete is slightly increased, whereas, the thermal conductivity is slightly decreased against the plain mortar irrespective of the length of the carbon fiber. In addition, a mixture of the graphite and carbon fiber can greatly improve the degree of heating test. CONCLUSIONS : Various properties of cement mortar change with the use of carbon fiber or graphite. To enhance the conductivity of concrete for deicing during winter, both carbon fiber and graphite are required to be used simultaneously.

Measurement of Electrical Conductivity of Glass Melter at High Temperature (유리 용융물의 고온에서 전기 전도도 측정)

  • Kim, Taesam;Kil, Daesup;Jung, Hunsaeng;Kang, Eunhee;Yoon, Soksung
    • Analytical Science and Technology
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    • v.13 no.6
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    • pp.775-780
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    • 2000
  • The electrical conductivity of glass melter at high temperature has been measured. The conductivity is an important physical property for the research and the manufacturing process of glass. Because high temperature is an inconvenient situation to measure the conductivity of glass melter, we have made a platinum crucible and electrode and have measured the conductivity at high temperature. KCl solution, of which concentration is adjusted to the conductivity of glass melter, is used to get parameters of the conductivity cell. A measuring circuit is composed with an AC 1 kHz sine wave generator and an operational amplifier. The cell constants are determined from the measured voltages and the equivalent conductances of KCl solution. Various cells are tested to find a suitable shape for high temperature experiment. The results are compared by cell size, electrode depth, and cell configuration. The conductivity of the borosilicate melter is $0.053{\Omega}^{-1}cm^{-1}$ at $1,450^{\circ}C$.

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Effect of Thermal Grease on Thermal Conductivity for Mild Steel and Stainless Steel by ASTM D5470 (ASTM D5470 방법으로 연강과 스테인리스강의 열전도도 측정시 열그리스의 영향)

  • Cho, Young-Wook;Hahn, Byung-Dong;Lee, Ju Ho;Park, Sung Hyuk;Baeg, Ju-Hwan;Cho, Young-Rae
    • Korean Journal of Materials Research
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    • v.29 no.7
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    • pp.443-450
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    • 2019
  • Thermal management is a critical issue for the development of high-performance electronic devices. In this paper, thermal conductivity values of mild steel and stainless steel(STS) are measured by light flash analysis(LFA) and dynamic thermal interface material(DynTIM) Tester. The shapes of samples for thermal property measurement are disc type with a diameter of 12.6 mm. For samples with different thickness, the thermal diffusivity and thermal conductivity are measured by LFA. For identical samples, the thermal resistance($R_{th}$) and thermal conductivity are measured using a DynTIM Tester. The thermal conductivity of samples with different thicknesses, measured by LFA, show similar values in a range of 5 %. However, the thermal conductivity of samples measured by DynTIM Tester show widely scattered values according to the application of thermal grease. When we use the thermal grease to remove air gaps, the thermal conductivity of samples measured by DynTIM Tester is larger than that measured by LFA. But, when we did not use thermal grease, the thermal conductivity of samples measured by DynTIM Tester is smaller than that measured by LFA. For the DynTIM Tester results, we also find that the slope of the graph of thermal resistance vs. thickness is affected by the usage of thermal grease. From this, we are able to conclude that the wide scattering of thermal conductivity for samples measured with the DynTIM Tester is caused by the change of slope in the graph of thermal resistance-thickness.

Sensitivity Analysis of Artificial Recharge in Consideration of Hydrogeologic Characteristics of Facility Agricultural Complex in Korea : Hydraulic Conductivity and Separation Distance from Injection Well to Pumping Well (국내 시설농업단지의 수리지질 특성을 고려한 인공함양 민감도 분석 : 수리전도도 및 주입정과 양수정의 이격거리)

  • Choi, Jung Chan;Kang, Dong-hwan
    • Journal of Environmental Science International
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    • v.28 no.9
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    • pp.737-749
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    • 2019
  • In this study, the sensitivity analysis of hydraulic conductivity and separation distance (distance between injection well and pumping well) was analyzed by establishing a conceptual model considering the hydrogeologic characteristics of facility agricultural complex in Korea. In the conceptual model, natural characteristics (topography and geology, precipitation, hydraulic conductivity, etc.) and artificial characteristics (separation distance from injection well to pumping well, injection rate and pumping rate, etc.) is entered, and sensitivity analysis was performed 12 scenarios using a combination of hydraulic conductivity ($10^{-1}cm/sec$, $10^{-2}cm/sec$, $10^{-3}cm/sec$, $10^{-4}cm/sec$) and separation distance (10 m, 50 m, 100 m). Groundwater drawdown at the monitoring well was increased as the hydraulic conductivity decreased and the separation distance increased. From the regression analysis of groundwater drawdown as a hydraulic conductivity at the same separation distance, it was found that the groundwater level fluctuation of artificial recharge aquifer was dominantly influenced by hydraulic conductivity. In the condition that the hydraulic conductivity of artificial recharge aquifer was $10^{-2}cm/sec$ or more, the radius of influence of groundwater level was within 20 m, but In the condition that the hydraulic conductivity is $10^{-3}cm/sec$ or less, it is confirmed that the radius of influence of groundwater increases sharply as the separation distance increases.

UNCERTAINTIES INVOLVED IN THE IONOSPHERIC CONDUCTIVITY ESTIMATION (전리층 전기전도도의 추정과 관련된 불확실성)

  • 곽영실;안병호
    • Journal of Astronomy and Space Sciences
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    • v.19 no.4
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    • pp.243-254
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    • 2002
  • Various uncertainties involved in ionospheric conductivity estimation utilizing the electron density profile obtained from the Sondrestrom incoherent scatter radar are examined. First, we compare the conductivity which is based on raw electron density and the one based on corrected electron density that takes into account the effects of the difference between the electron and ion temperatures and the Debye length. The corrected electron density yields higher Pedersen and Hall conductivities than the raw electron density does. Second, the dependence of collision frequency model on the conductivity estimation is examined. Below 110 km conductivity does not depend significantly on collision frequency models. Above 110 km, however, the collision models affect the conductivity estimation. Third, the influence of the electron and ion temperatures on the conductivity estimation is examined. Electron and ion temperatures carrying an error of about 10% do not seem to affect significantly the conductivity estimation. Fourth, also examined is the effect of the choice of the altitude range of integration in calculating the height-integrated conductivity, conductance. It has been demonstrated that the lower and upper boundaries of the integration are quite sensitive to the estimation of the Hall and Pedersen conductances, respectively.