• Title, Summary, Keyword: conductivity

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Thermal conductivity of rocks for geothermal energy utilization (지열에너지 활용을 위한 암석의 열전도도 고찰)

  • Lee, Young-Min
    • Transactions of the Korea Society of Geothermal Energy Engineers
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    • v.3 no.2
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    • pp.9-15
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    • 2007
  • Thermal conductivity of rocks is one of the most important parameters in designing a geothermal heat pump system, because heat exchange rate depends primarily on thermal conductivity of rocks. In this paper, the measurement methods of thermal conductivity, thermal conductivity of rocks, and heat exchange rate are discussed.

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Thermal transport study in actinide oxides with point defects

  • Resnick, Alex;Mitchell, Katherine;Park, Jungkyu;Farfan, Eduardo B.;Yee, Tien
    • Nuclear Engineering and Technology
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    • v.51 no.5
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    • pp.1398-1405
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    • 2019
  • We use a molecular dynamics simulation to explore thermal transport in oxide nuclear fuels with point defects. The effect of vacancy and substitutional defects on the thermal conductivity of plutonium dioxide and uranium dioxide is investigated. It is found that the thermal conductivities of these fuels are reduced significantly by the presence of small amount of vacancy defects; 0.1% oxygen vacancy reduces the thermal conductivity of plutonium dioxide by more than 10%. The missing of larger atoms has a more detrimental impact on the thermal conductivity of actinide oxides. In uranium dioxide, for example, 0.1% uranium vacancies decrease the thermal conductivity by 24.6% while the same concentration of oxygen vacancies decreases the thermal conductivity by 19.4%. However, uranium substitution has a minimal effect on the thermal conductivity; 1.0% uranium substitution decreases the thermal conductivity of plutonium dioxide only by 1.5%.

The Effects of Solution Heat Treatment and Aging Treatment on the Electrical Conductivity and Hardness of Cu-Cr Alloys (크롬동합금의 도전율과 경도에 미치는 용체화처리와 시효처리의 영향)

  • Kim, Shin Woo
    • Journal of the Korean Society for Heat Treatment
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    • v.15 no.1
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    • pp.21-24
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    • 2002
  • The electrode materials for welding machine in automobile industry such as Cu-Cr, Cu-Zr and Cu-$Al_2O_3$ require the high electrical conductivity and the proper hardness. Therefore the effects of solution heat treatment and aging treatment on the electrical conductivity and hardness of Cu-0.8wt%Cr and Cu-1.2wt%Cr alloys have been investigated. Cu-0.8wt%Cr alloy showed the higher electrical conductivity and hardness than Cu-1.2wt%Cr alloy and both alloys showed the better electrical conductivity at $930^{\circ}C$ among 930, 980 and $1030^{\circ}C$ solution heat treatment temperatures. The electrical conductivity and hardness in both alloys were not affected by aging treatment but remarkably affected by solution heat treatment temperature. The final drawing process reduced electrical conductivity and increased hardness more in Cu-1.2wt%Cr alloy.

Groundwater Characterization according to Hydraulic Conductivity Input Method (수리전도도 적용 방식에 따른 지하수특성 분석)

  • Ahn, Seung-Seop;Park, Dong-Il
    • Journal of Environmental Science International
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    • v.24 no.7
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    • pp.939-946
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    • 2015
  • Hydraulic conductivity is an important parameter in the analytical model of groundwater. This study analyzed the groundwater movement characteristics by estimating optimal parameters according to hydraulic conductivity input methods with the MODFLOW model which is widely used. It first estimated the optimal parameters by dividing hydraulic conductivity zones by attitude. Next, it estimated optimal parameters by geological characteristic. It analyzed the groundwater movement characteristics by applying the recharge quantity and amount of evapotranspiration of drought periods and flood years with the estimated parameters. As the result was analyzed that there are differences of observation water level values according to hydraulic conductivity input methods but there is no big differences of overall groundwater movement characteristics by hydraulic conductivity input method, the two methods have found to be applicability in analyses of groundwater. So, it is judged that studies on more exact application of hydraulic conductivity and the application methods are needed.

High Thermal Conductivity Silicon Nitride Ceramics

  • Hirao, Kiyoshi;Zhou, You;Hyuga, Hideki;Ohji, Tatsuki;Kusano, Dai
    • Journal of the Korean Ceramic Society
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    • v.49 no.4
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    • pp.380-384
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    • 2012
  • This paper deals with the recent developments of high thermal conductivity silicon nitride ceramics. First, the factors that reduce the thermal conductivity of silicon nitride are clarified and the potential approaches to realize high thermal conductivity are described. Then, the recent achievements on the silicon nitride fabricated through the reaction bonding and post sintering technique are presented. Because of a smaller amount of impurity oxygen, the obtained thermal conductivity is substantially higher, compared to that of the conventional gas-pressure sintered silicon nitride, while the microstructures and bending strengths are similar to each other between these two samples. Moreover, further improvement of the thermal conductivity is possible by increasing ${\beta}/{\alpha}$ phase ratio of the nitrided sample, resulting in a very high thermal conductivity of 177 W/($m{\cdot}K$) as well as a high fracture toughness of 11.2 $MPa{\cdot}m^{1/2}$.

Experimental Study on Thermal Conductivity of Concrete (콘크리트의 열전도율에 관한 실험적 연구)

  • 김국한;전상은;방기성;김진근
    • Journal of the Korea Concrete Institute
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    • v.13 no.4
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    • pp.305-313
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    • 2001
  • Conductivity is an important thermal property which governs heat transfer in a solid medium. Generally, the determination of conductivity in concrete is very difficult, because concrete is a heterogeneous material composed of cement, water, aggregate, et cetera and time dependent material of which properties change with curing age. In this study, influencing factors on thermal conductivity of concrete are quantitatively investigated by QTM-D3, a conductivity tester developed in Japan. Then, a prediction equation of thermal conductivity of concrete is suggested from the regression analysis of test results. To consider the factors influencing thermal conductivity of concrete, mortar, and cement paste, seven testing variables (age, amount of cement, types of admixtures, amount of coarse aggregate, fine aggregate ratio, temperature, and humidity condition) of the specimens are used. According to the experimental results, the amount of coarse aggregate and humidity condition of specimen are the main factors affecting the conductivity of concrete. Meanwhile, the conductivity of mortar and cement paste is strongly affected by the amount of cement and types of admixtures. However, the curing age has minor effect on the conductivity variation. Finally, the prediction formula of concrete conductivity as a function of aggregate amount, fine aggregate ratio, specimen temperature, and humidity condition is developed.

Determination of Freshness of Fish Meat using Electric Conductivity Meter (전기전도도를 이용한 어육의 선도판정)

  • LEE Byeong-HO
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.22 no.5
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    • pp.219-227
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    • 1989
  • A new devised conductivity meter was used in the rapid and convinient determination of freshness of fish meats. Electric conductivity of frozen fishes like cod, tuna, flounder, Alaksa pollock were demonstrated about $6,100\pm200{\mu}u$ at the beginning of spoilage showed VBN content of $30\~35mg\%$ while that of fresh meat of yellow tail, rock trout, and mackerel were in the range of $5,100\~5,400{\mu}u$. The relationship between electric conductivity and freshness as measured by VBN content was direct proportion during the deterioration of fish meat. It was presumed that electric conductivity change of red muscled fish was more temperature dependence than that of white muscled fishes. $Q_{10}$ value of mackerel meat was about 2.34 at the temperature ranged from 15 to $30^{\circ}C(\pm1^{\circ}C)$). The electric conductivity obtained with conductivity meter could be a valuable criteria for the freshness test of fish meat determining in 10 seconds by handy compact portable meter.

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An Experiment for determining Electrical Conductivity in Modelholes using Continuous Measurement System (공내수 전기전도도의 자동측정시스템 구축을 위한 실험)

  • 김영화;박정빈;임헌태
    • The Journal of Engineering Geology
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    • v.13 no.3
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    • pp.281-292
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    • 2003
  • We setup a continuous measurement system for electrical conductivity of fluid in a model borehole and verified the basic environments in electrical conductivity measurement for estimating hydraulic constants. The experiment was made by monitoring the conductivity change within the hole using NaCI solution of different salinities and incoming formation fluid using distilled water. The experiment was made under the state of constant flow rate by maintaining balance between inflow and outflow. Conductivity variation features were observed by controlling salinity contrasts and temperature differences between fluid within the hole and incoming formation fluid. flow rate and the location of inlet and outlet. The results of the experiment show well the role of each affecting factor on the conductivity distribution. and suggest appropriate environments for conductivity measurements. It is considered that the basis of the conductivity measurement for henceforward laboratory model and/or in-situ borehole experiment has been prepared.

Modeling on thermal conductivity of MOX fuel considering its microstructural heterogeneity

  • Lee, Byung-Ho;Koo, Yang-Hyun;Sohn, Dong-Seong
    • Proceedings of the Korean Nuclear Society Conference
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    • pp.247-247
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    • 1999
  • This paper describes a new mechanistic thermal conductivity model considering the heterogeneous microstructure of MOX fuel. Even though the thermal conductivities of MOX have been investigated numerously by experimental measurements and theoretical analyses, they show the large scattering making the performance analysis of MOX fuel difficult. Therefore, a thermal conductivity model that depends on the heterogeneous microstructure of MOX fuel has been developed by using a general two-phase thermal conductivity model. In order to apply this model for developing the thermal conductivity for heterogeneous MOX fuel, the fuel is assumed to consist of Purich particles and U02 matrix including Pu02 in solid solution. Since little relevant data on Purich particles is available, FIGARO and SiemensKWU results are only used to characterize the microstructure of unirradiated and irradiated fuel. Philliponneaus and HALDEN models are selected for the local thermal conductivities for Purich particles and matrix, respectively. Then by combining the two models, overall thermal conductivity of MOX fuel is obtained. The new proposed model estimates the MOX thermal conductivity about 10% less than the value of U02 fuel, which is in the range of MOX thermal conductivity from HALDEN. The developed thermal conductivity model has been incorporated into KAERIs fuel performance code, COSMOS, and then verified using the measured data in the FIGARO program. Comparison of predicted and measured temperatures shows the reasonable agreement within acceptable error bounds together with satisfactory results for the fission gas release and gap pressure.essure.

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CoReHA: conductivity reconstructor using harmonic algorithms for magnetic resonance electrical impedance tomography (MREIT)

  • Jeon, Ki-Wan;Lee, Chang-Ock;Kim, Hyung-Joong;Woo, Eung-Je;Seo, Jin-Keun
    • Journal of Biomedical Engineering Research
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    • v.30 no.4
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    • pp.279-287
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    • 2009
  • Magnetic resonance electrical impedance tomography (MREIT) is a new medical imaging modality providing cross-sectional images of a conductivity distribution inside an electrically conducting object. MREIT has rapidly progressed in its theory, algorithm and experimental technique and now reached the stage of in vivo animal and human experiments. Conductivity image reconstructions in MREIT require various steps of carefully implemented numerical computations. To facilitate MREIT research, there is a pressing need for an MREIT software package with an efficient user interface. In this paper, we present an example of such a software, called CoReHA which stands for conductivity reconstructor using harmonic algorithms. It offers various computational tools including preprocessing of MREIT data, identification of boundary geometry, electrode modeling, meshing and implementation of the finite element method. Conductivity image reconstruction methods based on the harmonic $B_z$ algorithm are used to produce cross-sectional conductivity images. After summarizing basics of MREIT theory and experimental method, we describe technical details of each data processing task for conductivity image reconstructions. We pay attention to pitfalls and cautions in their numerical implementations. The presented software will be useful to researchers in the field of MREIT for simulation as well as experimental studies.