• Asian Pacific Journal of Cancer Prevention
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• v.15 no.3
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• pp.1327-1331
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• 2014

Background: Electrical impedance tomography (EIT) is a new non-invasive, mobile screening method which does not use ionizing radiation to the human breast; allows conducting quantitative assessment of the images besides the visual interpretation. The aim of this study was to correlate the quantitative assessment and visual interpretation of breast electrical impedance tomographs and associated factors. Materials and Methods: One hundred and fifty mammography patients above 40 years and undergoing EIT were chosen using convenient sampling. Visual interpretation of the images was carried out by a radiologist with minimum of three years experience using the breast imaging - electrical impedance (BI-EIM) classification for detection of abnormalities. A set of thirty blinded EIT images were reinterpreted to determine the intra-rater reliability using kappa. Quantitative assessment was by comparison of the breast average electric conductivity with the norm and correlations with visual interpretation of the images were determined using Chi-square. One-way ANOVA was used to compare the mean electrical conductivity between groups and t-test was used for comparisons with pre-existing Caucasians statistics. Independent t-tests were applied to compare the mean electrical conductivity of women with factors like exogenous hormone use and family history of breast cancer. Results: The mean electrical conductivity of Malaysian women was significantly lower than that of Caucasians (p<0.05). Quantitative assessment of electrical impedance tomography was significantly related with visual interpretation of images of the breast (p<0.05). Conclusions: Quantitative assessment of electrical impedance tomography images was significantly related with visual interpretation.

• Journal of the Korean Geotechnical Society
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• v.31 no.6
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• pp.45-58
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• 2015

The aim of this study is to suggest a semi-empirical equation for estimating the hydraulic conductivity of sands using geoelectrical measurements technique. The suggested formula is based on the original Kozeny-Carman equation; therefore varying factors affecting the Kozeny-Carman equation were selected as the testing variables, and six different sands with varying particle sizes and particle shapes were used as the testing materials in this study. To measure both hydraulic and electrical conductivities, a series of constant head permeameter tests equipped with the four electrodes conductivity probe was conducted. Test results reveal that the effects of both pore water conductivity and flow rate in relation between hydraulic conductivity and formation factor (=pore water conductivity / measused conductivity of soil) of tested materials are negligible. However, because the variations of hydraulic conductivity of the tested sands according to particle sizes are significant, the estimated hydraulic conductivity using the formation factor varies with particle sizes. The overall comparison between the measured hydraulic conductivity and the estimated hydraulic conductivity using the suggested formula shows a good agreement, and the variation of hydraulic conductivity with varying Archie's m exponents is smaller compared with varying porosities.

• Journal of electromagnetic engineering and science
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• v.14 no.3
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• pp.293-298
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• 2014

Large spaceborne antennas should be lightweight, a factor related to the development costs of launch vehicles. In order to overcome this drawback, a feasibility study of a new carbon fiber reinforced polymer (CFRP) named M55J/RS3 is carried out for a synthetic aperture radar (SAR) reflector antenna. In particular, the high resolution of detected images is taken into consideration. To validate the electrical performance, a test of the CFRP specimen is fabricated, and the transmission/reflection coefficients are measured using a standard X-band waveguide. Finally, the effective complex permittivity and effective electrical conductivity are derived from the obtained measured data. By applying the derived conductivity to the simulation of the radiation pattern, antenna gain, and beamwidth-instead of relying on the assumption of a perfect electric conductor-variations in electrical performance are also investigated and discussed.

• Restorative Dentistry and Endodontics
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• v.37 no.3
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• pp.149-154
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• 2012

Objectives: To evaluate the accuracy of the Root ZX in teeth with simulated root perforation in the presence of gel or liquid type endodontic irrigants, such as saline, 5.25% sodium hypochlorite (NaOCl), 2% chlorhexidine liquid, 2% chlorhexidine gel, and RC-Prep, and also to determine the electrical conductivities of these endodontic irrigants. Materials and Methods: A root perforation was simulated on twenty freshly extracted teeth by means of a small perforation made on the proximal surface of the root at 4 mm from the anatomic apex. Root ZX was used to locate root perforation and measure the electronic working lengths. The results obtained were compared with the actual working length (AWL) and the actual location of perforations (AP), allowing tolerances of 0.5 or 1.0 mm. Measurements within these limits were considered as acceptable. Chi-square test or the Fisher's exact test was used to evaluate significance. Electrical conductivities of each irrigant were also measured with an electrical conductivity tester. Results: The accuracies of the Root ZX in perforated teeth were significantly different between liquid types (saline, NaOCl) and gel types (chlorhexidine gel, RC-Prep). The accuracies of electronic working lengths in perforated teeth were higher in gel types than in liquid types. The accuracy in locating root perforation was higher in liquid types than gel types. 5.25% NaOCl had the highest electrical conductivity, whereas 2% chlorhexidine gel and RC-Prep gel had the lowest electrical conductivities among the five irrigants. Conclusions: Different canal irrigants with different electrical conductivities may affect the accuracy of the Root ZX in perforated teeth.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.202-210
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• 2005

In this study, the fly ash was employed as a possible alternative to the bentonite for its high sorption capacity against cationic heavy metal. To consider the constituents of barrier possibly used, the specimens were mixed with different material contents (fly ash : weathered soil : bentonite), then sorption test was performed. Also the specimens were molded on the wet side of optimum moisture contents like mixing ratio of sorption test and their hydraulic conductivities were measured in flexible-wall permeameters. And to confirm the effect of dissolved cations, the hydraulic conductivity tests were repeated by converting the permeant liquids from water to $Cd^{2+}$ solution. Finally, the Cd-concentration at the effluent was analyzed for 500hrs to compare the effectiveness of each specimen in contaminant retardation. Test results showed that the more the ratio of fly ash increase, the more Kd value increase, and the hydraulic conductivity of weathered soil/bentonite (95:5) mixture was the lowest $(2.9*10^{-8}cm/sec)$, and specimens made of fly ash and fly ash/weathered soil mixtures showed similar hydraulic conductivity. Although the permeant liquid was changed from water to $Cd^{2+}$ solution, the hydraulic conductivity of all specimens except for weathered soil maintained similarly like before. Consequently, the initial breakthrough point of Cd in weathered soil specimen was observed at about 5hrs after the test started while that of fly ash specimens was not observed during the whole test period of 500hrs. The results implied that fly ash had a sufficient retardation capacity against contaminant transport possibly by its high sorption capacity although it showed little effect on the reduction of hydraulic conductivity. Based on the test results, it could be concluded that the fly ash can be possibly used as a suitable barrier material in containment system to attenuate the contaminant transport for its high retardation capacity and for the low cost.

• Journal of the Korean Society for Heat Treatment
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• v.33 no.6
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• pp.284-289
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• 2020

Since the dissimilar bonded interface usually consists of intermetallic compounds (IMCs) layer and cracks, their mechanical and electrical properties can be influenced by microstructure at interface between two different metals. In this study, the friction welded Cu-Al busbar, which is widely used to connect a secondary battery and their component, is selected to analyze the influence of interfacial characteristic on their tensile strength and electric conductivity. Then, the electrical characteristics of Cu busbar and Cu-Al busbar were investigated by thermal flow analysis and temperature rise test. In addition, the relationship between the maximum saturation temperature and the electrical conductivity were discussed in terms of interfacial characteristics of the friction welded Cu-Al busbar.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.2
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• pp.142-147
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• 2005

In this work, a gel polymer electrolyte (GPE) was prepared using polyoxyalkylene glycol acrylate (POAGA) as a macromonomer LiCoO$_2$/GPE/graphite cells were prepared and their electrochemical properties were evaluated at various current densities and temperatures. The ionic conductivity of the GPE was more than 6.2${\times}$10$^{-3}$ S$.$$cm^{-1}$ / at room temperature. The GPE had good electrochemical stability up to 4.5 V vs. Li/Li$^{+}$. POAGA-based cells were showed good electrochemical performances such as rate capability, low-temperature performance, and cycleability. The cells, also, passed a safety test such as the overcharge and nail-penetration test.t.

• Journal of Powder Materials
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• v.20 no.4
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• pp.285-290
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• 2013

$Ti_2AlN$ composites are a laminated compounds that posses unique combination of typical ceramic properties and typical metallic(Ti alloy) properties. In this paper, the powder synthesis, SPS sintering, composite characteristics and machinability evaluation were systematically conducted. The random orientation characteristics and good crystallization of the $Ti_2AlN$ phase are observed. The electrical and thermal conductivity of $Ti_2AlN$ is higher than that of Ti6242 alloy. A machining test was carried out to compare the effect of material properties on micro electrical discharge drilling for $Ti_2AlN$ composite and Ti6242 alloy. Also, mixture table as a kind of tables of orthogonal arrays was used to know how parameter is main effective at experimental design. Consequently, hybrid $Ti_2AlN$ ceramic composites showed good machining time and electrode wear shape under micro ED-drilling process. This conclusion proves the feasibility in the industrial applications.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.301-301
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• 2003

In current study, Nanocomposites are reinforced with carbon nanofiber, carbon nanotube and SiC, etc. Since the nano reinforcements have the excellent mechanical, thermal and electrical properties compared with that of existing composites, it has lately attracted considerable attention in the various areas. Cu have been widely used as signal transmission materials for electrical electronic components owing to its high electrical conductivity. However, it's size have been limited to small ones due to its poor mechanical properties. Until now, strengthening of the copper alloy was obtained either by the solid solution and precipitation hardening by adding alloy elements or the work hardening by deformation process. Adding the alloy elements lead to reduction of electrical conductivity. In this aspect, if carbon nanofiber is used as reinforcement which have outstanding mechanical strength and electric conductivity, it is possible to develope Cu matrix nanocomposite having almost no loss of electric conductivity. It is expected to be innovative in electric conducting material market. The unidirectional alignment of carbon nanofiber is the most challenging task developing the cooer matrix composites of high strength and electric conductivity. In this study, the unidirectional alignment of carbon nanofibers which is used reinforced material are controlled by drawing process and align mechanism as well as optimized drawing process parameter are verified via numerical analysis. The materials used in this study were pure copper and the nanofibers of 150nm in diameter and of 10∼20$\mu\textrm{m}$ in length. The materials have been tested and the tensile strength was 75MPa with the elongation of 44% for the copper. it is assumed that carbon nanofiber behave like porous elasto-plastic materials. Compaction test was conducted to obtain constitutive properties of carbon nanofiber Optimal parameter for drawing process was obtained by analytical and numerical analysis considering the various drawing angles, reduction areas, friction coefficient, etc. The lower drawing angles and lower reduction areas provides the less rupture of co tube is noticed during the drawing process and the better alignment of carbon nanofiber is obtained.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.35-41
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• 2021

Silicon is a promising next-generation anode material for lithium-ion battery, and it has been studied for commercialization due to the high theoretical capacity. However, it has problems of the volume change during charge-discharge and the poor electrical conductivity. To solve these problems, formation of SiO2 and carbon coating on the surface of silicon crystal were performed to protect the side reaction and enhance the electrical conductivity of silicon. CNT and CNF were also added to mitigate the volume change and increase the conductivity. Physical properties of asprepared samples were analyzed by XRD, SEM, and EDS. Electrochemical characteristics were investigated by electrical conductivity measurement, EIS, CV and cycle performance test. (Si/SiO2/C)+CNT&CNF showed high electrical conductivity and low charge-transfer resistance, and the capacity was 1528 mAh/g at 1st cycle and 1055 mAh/g at 50th cycle with 83% capacity retention.