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Subject: search.filters.subject.Resistivity

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    Electrical resistivity survey for evaluating the undrained shear strength of soft Bangkok clay at some of the canal-side road investigation sites
    (2022-01-01)
    Chaiyaput, Salisa
    ;
    Sutti, Nut
    ;
    Suksawat, Taweephong
    ;
    Ayawanna, Jiratchaya
    A resistivity-undrained shear strength equation was proposed in this work to investigate the relationship between the undrained shear strength and electrical resistivity of soft Bangkok clay. The field vane shear and screw driving sounding tests were used to evaluate the undrained shear strength of the soft Bangkok clay from 10 field investigations of the canal-side roads. Meanwhile, the electrical resistivity was collected by the low-cost nondestructive resistivity survey method. The relationship between the measured resistivity corresponding to the undrained shear strength was expressed as a linear equation of S<inf>u</inf> = 7.061ρ with a high statistical correlation (96.20%) between the undrained shear strength and resistivity. The validation between the predicted undrained shear strength from the equation and the measured undrained shear strength from the field sites confirmed the statistically significant relation of data and the reliability of the proposed equation. By using this equation, it successfully predicted the undrained shear strength of the soft Bangkok clay at a depth of 4.00–10.00 m below the ground surface of canal-side roads (zones C, D, and E in the zonation map). The proposed new equation from the resistivity survey in this work, therefore, serves as an alternative tool to fast estimate the shear strength of soft soil in the large area for the preliminary evaluation of road construction.
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    Development of a Ternary Composite of PU Resin/Carbon Black/PZT for Mechanical Energy Harvesting Application
    (2018-01-01)
    Punsawat, Woratat
    ;
    Makcharoen, Worawut
    Today, rapid depletion of energy sources forces us to discover alternative sustainable electrical energy sources quickly. The aim of this work was to develop a ternary composite of PU resin/carbon black/PZT to be an efficient mechanical energy harvester. Specifically, this present work attempted to find the optimum weight ratio of a PU resin/carbon black/PZT composite that could provide the highest mechanical-to-electrical conversion efficiency. The PU resin was the main matrix. Carbon black (CB) was added to improve conductivity while still maintaining good casting property. Then, PZT was added to generate electricity. Testing several weight ratios of this composite, it was found that the samples ratio of 60:20:20 was optimum and able to generate an average voltage of 0.357 V/in2. This ternary composite material has a candidate to into a practical and efficient electrical energy harvester source.
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    New current-voltage transferring device with different metals
    (2015-09-01)
    Kando, Masaaki
    ;
    Pattanadech, Norasage
    A new concept of an electrical shunt with different materials (aluminum and copper) has been developed to be used as an alternative current measurement device. The device provides better current measurement characteristics compared with the conventional current measurement devices such as a shunt resistor with an ammeter or the multiple shunts consisting of molybdenum having a low temperature coefficient and a Rogowski coil with an integrated circuit. The currents in several electrical circuits have been measured using the developed current-voltage transferring device (CVTD) as voltages between the aluminum and copper elements. The measured voltages (V<inf>m</inf>) are proportional to measuring currents (I<inf>m</inf>), which is shown as the following the experimental equation V<inf>m</inf> [mV] =kI<inf>m</inf> [A], in which k is a coefficient depending on the configuration of the CVTD.
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    In vitro measurement of myocardial impedivity anisotropy with a miniature rectangular tube
    (2003-04-01)
    Tsai, Jang Zern
    ;
    Will, James A.
    ;
    Vorperian, Vicken R.
    ;
    Hubbard-Van Stelle, Scott
    ;
    Cao, Hong
    Due to rapid change of fiber orientation, it is difficult to measure myocardial impedivity separately in a longitudinal or transverse fiber direction without mutual influence in the two directions. Previously published values of the longitudinal and the transverse myocardial impedivity were derived indirectly from measurements that mixed the impedivity in all directions. Those values are questionable because the derivations were based on a simplified uniform myocardial fiber model. In this paper, a miniature rectangular tube was devised to facilitate direct measurement of myocardial impedivity in a uniform fiber direction. The average transverse-to-longitudinal ratio of the measured in vitro swine myocardial impedivity was about 1.66 from 1 Hz to 1 kHz and dropped to 1.25 at 1 MHz. The result is important for accurate modeling of the electrical property of myocardium in biomedical research of radio-frequency cardiac catheter ablation.
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    In-vivo measurement of swine myocardial resistivity
    (2002-04-30)
    Tsai, Jang Zern
    ;
    Will, James A.
    ;
    Stelle, Scott Hubbard Van
    ;
    Cao, Hong
    ;
    Tungjitkusolmun, Supan
    We used a four-terminal plunge probe to measure myocardial resistivity in two directions at three sites from the epicardial surface of eight open-chest pigs in-vivo at eight frequencies ranging from 1Hz to 1 MHz. We calibrated the plunge probe to minimize the error due to stray capacitance between the measured subject and ground. We calibrated the probe in saline solutions contained in a metal cup situated near the heart that had an electrical connection to the pig's heart. The mean of the measured myocardial resistivity was 319 Ω cm at 1 Hz down to 166 Ωcm at 1 MHz. Statistical analysis showed the measured myocardial resistivity of two out of eight pigs was significantly different from that of other pigs. The myocardial resistivity measured with the resistivity probe oriented along and across the epicardial fiber direction was significantly different at only one out of the eight frequencies. There was no significant difference in the myocardial resistivity measured at different sites.