• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1807-1813
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• 2018

In this paper, the fault line selection and location problems of single line-to-ground (SLG) fault in distribution network are addressed. Firstly, the adaptive filtering property for empirical mode decomposition is formulated. Then in view of the different characteristics showed by the intrinsic mode functions(IMF) under different fault inception angles obtained by empirical mode decomposition, the sign of peak value about the low-frequency IMF and the capacitance transient energy is chosen as the fault line selection criteria according to the different proportion occupied by the low-frequency components. Finally, the fault location is determined based upon the comparison result with adjacent fault passage indicators' (FPI) waveform on the strength of the interaction between the distribution terminal unit(DTU) and the FPI. Moreover, the logic nodes regarding to fault line selection and location are newly expanded according to IEC61850, which also provides reference to acquaint the DTU or FPI's function and monitoring. The simulation results validate the effectiveness of the proposed fault line selection and location methods.

• Journal of the Korea Society of Computer and Information
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• v.17 no.8
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• pp.107-114
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• 2012

We have developed a textile capacitive pressure sensor for smart gait analysis. The proposed system can convert sensor signal into step counts and pressure levels by different posture. To evaluate the performance of insole type textile capacitive sensor, we measured capacitance change by increment of weights from 10 kg to 100 kg with 10 kg increment using M1 class rectangular weights (four 20 kg weights and two 10 kg weights) which have ${\pm}10%$ tolerance. The result showed non-linearity characteristic of a general capacitive pressure sensor. The test was performed according to a test protocol for four different postures (sitting, standing, standing on a left leg and standing on a right leg) and different walking speeds (1 km/h and 4 km/h). Five healthy male subjects were participated in each test. As we expected, the pressure level was changed by pressure distribution according to posture. Also, developed textile pressure sensor showed higher recognition rate (average 98.06 %) than commercial pedometer at all walking speed. Therefore, the proposed step counts and posture monitoring system using conductive textile capacitive pressure sensor proved to be a reliable and useful tool for monitoring gait parameters.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.45-45
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• 2003

The aim of this study was the characterization and performance validation of new prototype avalanche photodiode (APD) arrays for positron emission tomography (PET). Two different APD array prototypes (noted A and B) developed by Radiation Monitoring Device (RMD) have been investigated. Principal characteristics of the two APD array were measured and compared. In order to characterize and evaluate the APD performance, capacitance, doping concentration, quantum efficiency, gain and dark current were measured. The doping concentration that shows the impurity distribution within an APD pixel as a function of depth was derived from the relationship between capacitance and bias voltage. Quantum efficiency was measured using a mercury vapor light source and a monochromator used to select a wavelength within the range of 300 to 700 nm. Quantum efficiency measurements were done at 500 V, for which the APD gain is equal to one. For the gain measurements, a pencil beam with 450 nm in wavelength was illuminating the center of each pixel. The APD dark currents were measured as a function of gain and bias. A linear fitting method was used to determine the value of surface and bulk leakage currents. Mean quantum efficiencies measured at 400 and 450 nm were 0.41 and 0.54, for array A, and 0.50 and 0.65 for array B. Mean gain at a bias voltage of 1700 V, was 617.6 for array A and 515.7 for type B. The values based on linear fitting were 0.08${\pm}$0.02 nA 38.40${\pm}$6.26 nA, 0.08${\pm}$0.0l nA 36.87${\pm}$5.19 nA, and 0.05${\pm}$0.00 nA, 21.80${\pm}$1.30 nA in bulk surface leakage current for array A and B respectively. Results of characterization demonstrate the importance of performance measurement validating the capability of APD array as the detector for PET imaging.

• Molecules and Cells
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• v.39 no.11
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• pp.807-813
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• 2016

Escherichia coli are important indicator organisms, used routinely for the monitoring of water and food safety. For quick, sensitive and real-time detection of E. coli we developed a 2'F modified RNA aptamer Ec3, by Cell-SELEX. The 31 nucleotide truncated Ec3 demonstrated improved binding and low nano-molar affinity to E. coli. The aptamer developed by us out-performs the commercial antibody and aptamer used for E. coli detection. Ec3(31) aptamer based E. coli detection was done using three different detection formats and the assay sensitivities were determined. Conventional Ec3(31)-biotin-streptavidin magnetic separation could detect E. coli with a limit of detection of $1.3{\times}10^6CFU/ml$. Although, optical analytic technique, biolayer interferometry, did not improve the sensitivity of detection for whole cells, a very significant improvement in the detection was seen with the E. coli cell lysate ($5{\times}10^4CFU/ml$). Finally we developed Electrochemical Impedance Spectroscopy (EIS) gap capacitance biosensor that has detection limits of $2{\times}10^4CFU/mL$ of E. coli cells, without any labeling and signal amplification techniques. We believe that our developed method can step towards more complex and real sample application.

• Journal of Sensor Science and Technology
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• v.27 no.6
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• pp.397-402
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• 2018

Proper seat design is critical to the safety, comfort, and ergonomics of automotive driver's seats. To ensure effective seat design, quantitative methods should be used to evaluate the characteristics of automotive seats. This paper presents a system that is capable of simultaneously monitoring body pressure distribution and surface deformation in a textile material. In this study, a textile-based capacitive sensor was used to detect the body pressure distribution in an automotive seat. In addition, a strain gauge sensor was used to detect the degree of curvature deformation due to high-pressure points. The textile-based capacitive sensor was fabricated from the conductive fabric and a polyurethane insulator with a high signal-to-noise ratio. The strain gauge sensor was attached on the guiding film to maximize the effect of its deformation due to bending. Ten pressure sensors were placed symmetrically in the hip area and six strain gauge sensors were distributed on both sides of the seat cushion. A readout circuit monitored the absolute and relative values from the sensors in realtime, and the results were displayed as a color map. Moreover, we verified the proposed system for quantifying the body pressure and fabric deformation by studying 18 participants who performed three predefined postures. The proposed system showed desirable results and is expected to improve seat safety and comfort when applied to the design of various seat types. Moreover, the proposed system will provide analytical criteria in the design and durability testing of automotive seats.

• Journal of the Korea Institute of Building Construction
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• v.22 no.6
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• pp.651-662
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• 2022

The electrochemical impedance spectroscopy(EIS) method was used to evaluate the concrete deterioration process related to chloride-induced steel corrosion with various corrosion levels(initiation, rust propagation and acceleration periods). The impressed current technique, with four total current levels of 0C, 13C, 65C and 130C, was used to accelerate steel corrosion in concrete cylinder samples with w/c ratio of 0.4, 0.5, and 0.6, immersed in a 0.5M NaCl solution. A series of EIS measurements was performed to monitor concrete deterioration during the accelerated corrosion test in this study. Some critical parameters of the equivalent circuit were obtained through the EIS analysis. It was observed that the charge transfer resistance(R_c) dropped sharply as the impressed current increased from 0C to 13C, indicating a value of approximately 10kΩcm². However, the sensitivity of R_c significantly decreased when the impressed current was further increased from 13C to 130C after corrosion of steel had been initiated. Meanwhile, the double-layer capacitance value(C_dl) linearly increased from 50×10^-6μF/cm² to 250×10^-6μF/cm² as the impressed current in creased from 0C to 130C. The results in this study showed that monitoring C_dl is an effective measurement parameter for evaluating the progress of internal concrete damages(de-bonding between steel and concrete, micro-cracks, and surface-breaking cracks) induced by steel corrosion. The findings of this study provide a fundamental basis for developing an embedded sensor and signal interpretation method for monitoring concrete deterioration due to steel corrosion at various corrosion levels.